US20160278178A1 - Led lighting systems and methods for constant current control in various operation modes - Google Patents

Abstract

System and method for providing at least an output current to one or more light emitting diodes. The system includes a control component configured to receive at least a demagnetization signal, a sensed signal and a reference signal and to generate a control signal based on at least information associated with the demagnetization signal, the sensed signal and the reference signal, and a logic and driving component configured to receive at least the control signal and output a drive signal to a switch based on at least information associated with the control signal. The switch is connected to a first diode terminal of a diode and a first inductor terminal of an inductor. The diode further includes a second diode terminal, and the inductor further includes a second inductor terminal.

Description

1. CROSS-REFERENCES TO RELATED APPLICATIONS
• This application claims priority to Chinese Patent Application No. 201110376439.0, filed Nov. 15, 2011, incorporated by reference herein for all purposes.
2. BACKGROUND OF THE INVENTION
• The present invention is directed to integrated circuits. More particularly, the invention provides lighting systems and methods for constant current control in various operation modes. Merely by way of example, the invention has been applied to one or more light emitting diodes. But it would be recognized that the invention has a much broader range of applicability.
• Generally, a conventional lighting system for light emitting diodes (LEDs) often uses a floating Buck converter. This type of LED lighting system usually is cost effective with compact size.FIG. 1 is a simplified diagram showing a conventional LED lighting system with a Buck converter. Thelighting system100 includes a pulse-width-modulation (PWM)controller110, apower switch120, adiode130, aninductor140,capacitors150 and152, and asensing resistor160. Additionally, thelighting system100 receives an input voltage and provides a lamp current and a lamp voltage to one ormore LEDs190.
• As shown inFIG. 1, thepower switch120 includesterminals122,124, and126. ThePWM controller110 outputs adrive signal112 and receives acurrent sensing signal114. Thedrive signal112 corresponds to a switching period (e.g., T_S). For example, thepower switch120 is a MOS transistor. In another example, thepower switch120 is a bipolar transistor (e.g. an NPN bipolar transistor). In yet another example, thepower switch120 is an insulated gate bipolar transistor (IGBT).
• It is highly desirable to improve the techniques of constant current control, so that a constant lamp current can be achieved in the DCM mode, the CCM mode and the critical conduction mode (CRM), and both high power factor and precision control can be realized.
3. BRIEF SUMMARY OF THE INVENTION
• The present invention is directed to integrated circuits. More particularly, the invention provides lighting systems and methods for constant current control in various operation modes. Merely by way of example, the invention has been applied to one or more light emitting diodes. But it would be recognized that the invention has a much broader range of applicability.
• According to another embodiment, a system for providing at least an output current to one or more light emitting diodes includes a control component configured to receive at least a demagnetization signal, a sensed signal and a reference signal and to generate a control signal based on at least information associated with the demagnetization signal, the sensed signal and the reference signal, and a logic and driving component configured to receive at least the control signal and output a drive signal to a switch based on at least information associated with the control signal. The switch is connected to a first diode terminal of a diode and a first inductor terminal of an inductor. The diode further includes a second diode terminal, and the inductor further includes a second inductor terminal. The second diode terminal and the second inductor terminal are configured to provide at least the output current to the one or more light emitting diodes. The control signal is configured to regulate the output current at a constant magnitude.
• According to yet another embodiment, a method for providing at least an output current to one or more light emitting diodes includes receiving at least a demagnetization signal, a sensed signal and a reference signal, processing information associated with the demagnetization signal, the sensed signal and the reference signal, and generating a control signal based on at least information associated with the demagnetization signal, the sensed signal and the reference signal. Additionally, the method includes receiving at least the control signal, processing information associated with the control signal, and outputting a drive signal to a switch connected to a first diode terminal of a diode and a first inductor terminal of an inductor. The diode further includes a second diode terminal, and the inductor further includes a second inductor terminal. The second diode terminal and the second inductor terminal are configured to provide at least the output current to the one or more light emitting diodes. Moreover, the method includes regulating the output current at a predetermined magnitude based on at least information associated with the control signal.
• According to yet another embodiment, a system for providing at least an output current to one or more light emitting diodes includes a first signal processing component configured to receive at least a sensed signal and generate a first signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the system includes a second signal processing component configured to generate a second signal, an integrator component configured to receive the first signal and the second signal and generate a third signal, and a comparator configured to process information associated with the third signal and the sensed signal and generate a comparison signal based on at least information associated with the third signal and the sensed signal. Moreover, the system includes a signal generator configured to receive at least the comparison signal and generate a modulation signal, and a gate driver configured to receive the modulation signal and output a drive signal to the switch. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period for the switch and a demagnetization period for a demagnetization process. For each of the one or more switching periods, the first signal represents a multiplication result of a first sum of the on-time period and the demagnetization period and a second sum of a first current magnitude and a second current magnitude, and the second signal represents the switching period multiplied by a predetermined current magnitude. The first current magnitude represents the inductor current at the beginning of the on-time period, and the second current magnitude represents the inductor current at the end of the on-time period. The integrator component is further configured to integrate period-by-period differences between the first signal and the second signal for a plurality of switching periods, and the third signal represents the integrated period-by-period differences. The integrated period-by-period differences are smaller than a predetermined threshold in magnitude.
• According to yet another embodiment, a method for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the method includes processing information associated with the sensed signal, generating a first signal based on at least information associated with the sensed signal, generating a second signal, receiving the first signal and the second signal, processing information associated with the first signal and the second signal, and generating a third signal based on at least information associated with the first signal and the second signal. Moreover, the method includes processing information associated with the third signal and the sensed signal, generating a comparison signal based on at least information associated with the third signal and the sensed signal, receiving at least the comparison signal, generating a modulation signal based on at least information associated with the comparison signal, receiving the modulation signal, and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period and a demagnetization period. For each of the one or more switching periods, the first signal represents a multiplication result of a first sum of the on-time period and the demagnetization period and a second sum of a first current magnitude and a second current magnitude, and the second signal represents the switching period multiplied by a predetermined current magnitude. The first current magnitude represents the inductor current at the beginning of the on-time period, and the second current magnitude represents the inductor current at the end of the on-time period. The process for processing information associated with the first signal and the second signal includes integrating period-by-period differences between the first signal and the second signal for a plurality of switching periods, and the third signal represents the integrated period-by-period differences. The integrated period-by-period differences are smaller than a predetermined threshold in magnitude.
• According to yet another embodiment, a system for providing at least an output current to one or more light emitting diodes includes a first signal processing component configured to receive at least a sensed signal and generate a first signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the system includes a second signal processing component configured to generate a second signal, an integrator component configured to receive the first signal and the second signal and generate a third signal, and a comparator configured to process information associated with the third signal and the sensed signal and generate a comparison signal based on at least information associated with the third signal and the sensed signal. Moreover, the system includes a signal generator configured to receive at least the comparison signal and generate a modulation signal, and a gate driver configured to receive the modulation signal and output a drive signal to the switch. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period for the switch and a demagnetization period for a demagnetization process. For each of the one or more switching periods, the first signal represents a sum of a first multiplication result and a second multiplication result, and the second signal represents the switching period multiplied by a predetermined current magnitude. The first multiplication result is equal to the on-time period multiplied by a sum of a first current magnitude and a second current magnitude. The first current magnitude represents the inductor current at the beginning of the on-time period, and the second current magnitude represents the inductor current at the end of the on-time period. The second multiplication result is equal to two multiplied by the demagnetization period and further multiplied by a third current magnitude, and the third current magnitude represents the inductor current at the middle of the on-time period. The integrator component is further configured to integrate period-by-period differences between the first signal and the second signal for a plurality of switching periods, and the third signal represents the integrated period-by-period differences. The integrated period-by-period differences are smaller than a predetermined threshold in magnitude.
• According to yet another embodiment, a method for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the method includes processing information associated with the sensed signal, generating a first signal based on at least information associated with the sensed signal, generating a second signal, receiving the first signal and the second signal, processing information associated with the first signal and the second signal, and generating a third signal based on at least information associated with the first signal and the second signal. Moreover, the method includes processing information associated with the third signal and the sensed signal, generating a comparison signal based on at least information associated with the third signal and the sensed signal, receiving at least the comparison signal, and generating a modulation signal based on at least information associated with the comparison signal. Also, the method includes receiving the modulation signal, and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period and a demagnetization period. For each of the one or more switching periods, the first signal represents a sum of a first multiplication result and a second multiplication result, and the second signal represents the switching period multiplied by a predetermined current magnitude. The first multiplication result is equal to the on-time period multiplied by a sum of a first current magnitude and a second current magnitude. The first current magnitude represents the inductor current at the beginning of the on-time period, and the second current magnitude represents the inductor current at the end of the on-time period. The second multiplication result is equal to two multiplied by the demagnetization period and further multiplied by a third current magnitude, and the third current magnitude represents the inductor current at the middle of the on-time period. The process for processing information associated with the first signal and the second signal includes integrating period-by-period differences between the first signal and the second signal for a plurality of switching periods, and the third signal represents the integrated period-by-period differences. The integrated period-by-period differences are smaller than a predetermined threshold in magnitude.
• According to yet another embodiment, a system for providing at least an output current to one or more light emitting diodes includes a first sampling-and-holding and voltage-to-current-conversion component configured to receive at least a sensed signal and generate a first current signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a first switch. Additionally, the system includes a second sampling-and-holding and voltage-to-current-conversion component configured to receive at least the sensed signal and generate a second current signal, and a signal-amplification and voltage-to-current-conversion component configured to receive at least the sensed signal and generate a third current signal. Moreover, the system includes a current-signal generator configured to generate a fourth current signal, and a capacitor coupled to the current-signal generator, coupled through a second switch to the first sampling-and-holding and voltage-to-current-conversion component and the second sampling-and-holding and voltage-to-current-conversion component, and coupled through a third switch to the signal-amplification and voltage-to-current-conversion component. The capacitor is configured to generate a voltage signal. Also, the system includes a comparator configured to process information associated with the voltage signal and the sensed signal and generate a comparison signal based on at least information associated with the voltage signal and the sensed signal. Additionally, the system includes a modulation-signal generator configured to receive at least the comparison signal and generate a modulation signal, and a gate driver configured to receive the modulation signal and output a drive signal to the first switch. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period for the first switch and a demagnetization period for a demagnetization process. The first current signal represents the inductor current at the beginning of the on-time period, the second current signal represents the inductor current at the end of the on-time period, and the third current signal represents the inductor current. For each of the one or more switching periods, the first current signal and the second current signal are configured to discharge or charge the capacitor during only the demagnetization period, the third current signal is configured to discharge or charge the capacitor during only the on-time period, and the fourth current signal is configured to charge or discharge the capacitor during the switching period.
• According to yet another embodiment, a method for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch, processing information associated with the sensed signal, and generating a first current signal, a second current signal, and a third current signal based on at least information associated with the sensed signal. Additionally, the method includes generating a fourth current signal, processing information associated with the first current signal, the second current signal, the third current signal, and the fourth current signal, and generating a voltage signal, by at least a capacitor, based on at least information associated with the first current signal, the second current signal, the third current signal, and the fourth current signal. Moreover, the method includes processing information associated with the voltage signal and the sensed signal, generating a comparison signal based on at least information associated with the voltage signal and the sensed signal, receiving at least the comparison signal, and generating a modulation signal based on at least information associated with the comparison signal. Also, the method includes receiving the modulation signal, and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period and a demagnetization period. The first current signal represents the inductor current at the beginning of the on-time period, the second current signal represents the inductor current at the end of the on-time period, and the third current signal represents the inductor current. For each of the one or more switching periods, the process for processing information associated with the first current signal, the second current signal, the third current signal, and the fourth current signal includes discharging or charging the capacitor with the first current signal and the second current signal during only the demagnetization period, discharging or charging the capacitor with the third current signal during only the on-time period, and charging or discharging the capacitor with the fourth current signal during the switching period.
• According to yet another embodiment, a system for providing at least an output current to one or more light emitting diodes includes a signal-amplification and voltage-to-current-conversion component configured to receive at least a sensed signal and generate a first current signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a first switch. Additionally, the system includes a current-signal generator configured to generate a second current signal, and a capacitor coupled to the current-signal generator, and coupled through a second switch to the signal-amplification and voltage-to-current-conversion component. The capacitor is configured to generate a voltage signal. Moreover, the system includes a comparator configured to process information associated with the voltage signal and the sensed signal and generate a comparison signal based on at least information associated with the voltage signal and the sensed signal, a modulation-signal generator configured to receive at least the comparison signal and generate a modulation signal, and a gate driver configured to receive the modulation signal and output a drive signal to the first switch. The drive signal is associated with at least one or more switching periods, and the first current signal represents the inductor current. Each of the one or more switching periods includes at least an on-time period for the first switch. For each of the one or more switching periods, the first current signal is configured to discharge or charge the capacitor during only the on-time period, and the second current signal is configured to charge or discharge the capacitor during only the on-time period.
• According to yet another embodiment, a method for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the method includes processing information associated with the sensed signal, generating a first current signal based on at least information associated with the sensed signal, generating a second current signal, processing information associated with the first current signal and the second current signal, and generating a voltage signal, by at least a capacitor, based on at least information associated with the first current signal and the second current signal. Moreover, the method includes processing information associated with the voltage signal and the sensed signal, generating a comparison signal based on at least information associated with the voltage signal and the sensed signal, receiving at least the comparison signal, generating a modulation signal based on at least information associated with the comparison signal, receiving the modulation signal, and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least one or more switching periods, and the first current signal represents the inductor current. Each of the one or more switching periods includes at least an on-time period. For each of the one or more switching periods, the process for processing information associated with the first current signal and the second current signal includes discharging or charging the capacitor with the first current signal during only the on-time period, and charging or discharging the capacitor with the second current signal during only the on-time period.
• According to yet another embodiment, a system for providing at least an output current to one or more light emitting diodes includes a transconductance amplifier configured to receive a sensed signal and also receive a predetermined voltage signal through a first switch. The sensed signal is associated with an inductor current flowing through an inductor coupled to a second switch, and the transconductance amplifier is further configured to generate a current signal. Additionally, the system includes a capacitor coupled to the transconductance amplifier and configured to generate a voltage signal, and a comparator configured to process information associated with the voltage signal and the sensed signal and generate a comparison signal based on at least information associated with the voltage signal and the sensed signal. Moreover, the system includes a modulation-signal generator configured to receive at least the comparison signal and generate a modulation signal, and a gate driver configured to receive the modulation signal and output a drive signal to the second switch. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period for the second switch. The transconductance amplifier is further configured to, for each of the one or more switching periods, receive at least a predetermined voltage signal only during the on-time period. The current signal is configured to charge or discharge the capacitor.
• According to yet another embodiment, a method for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the method includes processing information associated with the sensed signal and a predetermined voltage signal, generating a current signal based on at least information associated with the sensed signal and the predetermined voltage signal, and processing information associated with the current signal. Moreover, the method includes generating a voltage signal, by at least a capacitor, based on at least information associated with the current signal, processing information associated with the voltage signal and the sensed signal, and generating a comparison signal based on at least information associated with the voltage signal and the sensed signal. Also, the method includes receiving at least the comparison signal, generating a modulation signal based on at least information associated with the comparison signal, receiving the modulation signal, and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period. The process for receiving at least a sensed signal includes, for each of the one or more switching periods, receiving at least the predetermined voltage signal during only the on-time period. Also, the process for processing information associated with the current signal includes charging or discharging the capacitor with the current signal.
• According to yet another embodiment, a system for providing at least an output current to one or more light emitting diodes includes a first sampling-and-holding and voltage-to-current-conversion component configured to receive at least a sensed signal and generate a first current signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a first switch. Additionally, the system includes a second sampling-and-holding and voltage-to-current-conversion component configured to receive at least the sensed signal and generate a second current signal, and a signal-amplification and voltage-to-current-conversion component configured to receive at least the sensed signal and generate a third current signal, a current-signal generator configured to generate a fourth current signal, and a capacitor coupled to the current-signal generator, coupled through a second switch to the first sampling-and-holding and voltage-to-current-conversion component and the second sampling-and-holding and voltage-to-current-conversion component, and coupled through a third switch to the signal-amplification and voltage-to-current-conversion component, the capacitor being configured to generate a first voltage signal. Moreover, the system includes a multiplier component configured to process information associated with the first voltage signal and a second voltage signal and generate a multiplication signal based on at least information associated with the first voltage signal and the second voltage signal. Also, the system includes a comparator configured to receive the multiplication signal and the sensed signal and generate a comparison signal based on at least information associated with the multiplication signal and the sensed signal, a modulation-signal generator configured to receive at least the comparison signal and generate a modulation signal, and a gate driver configured to receive the modulation signal and output a drive signal to the first switch. The drive signal is associated with at least a plurality of switching periods, and each of the one or more switching periods includes at least an on-time period for the first switch and a demagnetization period for a demagnetization process. The first current signal represents the inductor current at the beginning of the on-time period, the second current signal represents the inductor current at the end of the on-time period, and the third current signal represents the inductor current. For the plurality of switching periods, the first current signal and the second current signal are configured to discharge or charge the capacitor during only the demagnetization period, the third current signal is configured to discharge or charge the capacitor during only the on-time period, and the fourth current signal is configured to charge or discharge the capacitor during the switching period.
• According to yet another embodiment, a method for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the method includes processing information associated with the sensed signal, and generating a first current signal, a second current signal, and a third current signal based on at least information associated with the sensed signal. Moreover, the method includes generating a fourth current signal, processing information associated with the first current signal, the second current signal, the third current signal, and the fourth current signal, and generating a first voltage signal, by at least a capacitor, based on at least information associated with the first current signal, the second current signal, the third current signal, and the fourth current signal. Also, the method includes processing information associated with the first voltage signal and a second voltage signal, generating a multiplication signal based on at least information associated with the first voltage signal and the second voltage signal, receiving the multiplication signal and the sensed signal, and generating a comparison signal based on at least information associated with the multiplication signal and the sensed signal. Additionally, the method includes receiving at least the comparison signal, generating a modulation signal based on at least information associated with the comparison signal, receiving the modulation signal, and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least a plurality of switching periods, and each of the plurality of switching periods includes at least an on-time period and a demagnetization period. The first current signal represents the inductor current at the beginning of the on-time period, the second current signal represents the inductor current at the end of the on-time period, and the third current signal represents the inductor current. For each of the plurality of switching periods, the process for processing information associated with the first current signal, the second current signal, the third current signal, and the fourth current signal includes discharging or charging the capacitor with the first current signal and the second current signal during only the demagnetization period, discharging or charging the capacitor with the third current signal during only the on-time period, and charging or discharging the capacitor with the fourth current signal during the switching period.
• According to yet another embodiment, a system for providing at least an output current to one or more light emitting diodes includes a transconductance amplifier configured to receive a sensed signal and also receive a predetermined voltage signal through a first switch. The sensed signal is associated with an inductor current flowing through an inductor coupled to a second switch, and the transconductance amplifier is further configured to generate a current signal. Additionally, the system includes a capacitor coupled to the transconductance amplifier and configured to generate a voltage signal, and a comparator configured to process information associated with the voltage signal and a ramping signal and generate a comparison signal based on at least information associated with the voltage signal and the ramping signal. Moreover, the system includes a modulation-signal generator configured to receive at least the comparison signal and generate a modulation signal, and a gate driver configured to receive the modulation signal and output a drive signal to the second switch. The drive signal is associated with at least one or more switching periods, each of the one or more switching periods including at least an on-time period for the second switch. The transconductance amplifier is further configured to, for each of the one or more switching periods, receive at least a predetermined voltage signal only during the on-time period. The current signal is configured to charge or discharge the capacitor.
• According to yet another embodiment, a method for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the method includes processing information associated with the sensed signal and a predetermined voltage signal, generating a current signal based on at least information associated with the sensed signal and the predetermined voltage signal, processing information associated with the current signal, and generating a voltage signal, by at least a capacitor, based on at least information associated with the current signal. Moreover, the method includes processing information associated with the voltage signal and a ramping signal, generating a comparison signal based on at least information associated with the voltage signal and the ramping signal, receiving at least the comparison signal, and generating a modulation signal based on at least information associated with the comparison signal. Also, the method includes receiving the modulation signal and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period. The process for receiving at least a sensed signal includes, for each of the one or more switching periods, receiving at least a predetermined voltage signal only during the on-time period, and the process for processing information associated with the current signal includes charging or discharging the capacitor with the current signal.
• According to yet another embodiment, a system for providing at least an output current to one or more light emitting diodes includes a transconductance amplifier configured to receive a sensed signal and also receive a predetermined voltage signal through a first switch. The sensed signal is associated with an inductor current flowing through an inductor coupled to a second switch, and the transconductance amplifier is further configured to generate a current signal. Additionally, the system includes a capacitor coupled to the transconductance amplifier and configured to generate a first voltage signal, and a multiplier component configured to process information associated with the first voltage signal and a second voltage signal and generate a multiplication signal based on at least information associated with the first voltage signal and the second voltage signal. Moreover, the system includes a comparator configured to receive the multiplication signal and the sensed signal and generate a comparison signal based on at least information associated with the multiplication signal and the sensed signal, a modulation-signal generator configured to receive at least the comparison signal and generate a modulation signal, and a gate driver configured to receive the modulation signal and output a drive signal to the second switch. The drive signal is associated with at least one or more switching periods, each of the one or more switching periods including at least an on-time period for the second switch. The transconductance amplifier is further configured to, for each of the one or more switching periods, receive at least a predetermined voltage signal during only the on-time period. The current signal is configured to charge or discharge the capacitor.
• According to yet another embodiment, a method for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the method includes processing information associated with the sensed signal and a predetermined voltage signal, generating a current signal based on at least information associated with the sensed signal and the predetermined voltage signal, processing information associated with the current signal, and generating a first voltage signal, by at least a capacitor, based on at least information associated with the current signal. Moreover, the method includes processing information associated with the first voltage signal and a second voltage signal, generating a multiplication signal based on at least information associated with the first voltage signal and the second voltage signal, receiving the multiplication signal and the sensed signal, and generating a comparison signal based on at least information associated with the multiplication signal and the sensed signal. Also, the method includes receiving at least the comparison signal, generating a modulation signal based on at least information associated with the comparison signal, receiving the modulation signal, and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period. The process for receiving at least a sensed signal includes, for each of the one or more switching periods, receiving at least a predetermined voltage signal during only the on-time period, and the process for processing information associated with the current signal includes charging or discharging the capacitor with the current signal.
• According to yet another embodiment, a system for providing at least an output current to one or more light emitting diodes includes a first signal processing component configured to receive at least a sensed signal and generate a first signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the system includes a second signal processing component configured to generate a second signal, an integrator component configured to receive the first signal and the second signal and generate a third signal, a comparator configured to process information associated with the third signal and the sensed signal and generate a comparison signal based on at least information associated with the third signal and the sensed signal. Moreover, the system includes a signal generator configured to receive at least the comparison signal and generate a modulation signal, and a gate driver configured to receive the modulation signal and output a drive signal to the switch. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period for the switch and a demagnetization period for a demagnetization process. The first signal processing component is further configured to, for each of the one or more switching periods, sample the sensed signal at the middle of the on-time period, hold the sampled sensed signal representing the inductor current at the middle of the on-time period, and generate the first signal representing a sum of a first multiplication result and a second multiplication result based on at least information associated with the held and sampled sensed signal. For each of the one or more switching periods, the second signal represents the switching period multiplied by a predetermined current magnitude. The integrator component is further configured to integrate period-by-period differences between the first signal and the second signal for a plurality of switching periods, and the third signal represents the integrated period-by-period differences. The integrated period-by-period differences are smaller than a predetermined threshold in magnitude.
• According to yet another embodiment, a method for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the method includes processing information associated with the sensed signal, generating a first signal based on at least information associated with the sensed signal, generating a second signal, receiving the first signal and the second signal, processing information associated with the first signal and the second signal, and generating a third signal based on at least information associated with the first signal and the second signal. Moreover, the method includes processing information associated with the third signal and the sensed signal, generating a comparison signal based on at least information associated with the third signal and the sensed signal, receiving at least the comparison signal, and generating a modulation signal based on at least information associated with the comparison signal. Also, the method includes receiving the modulation signal, and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period for the switch and a demagnetization period for a demagnetization process. The process for processing information associated with the sensed signal includes, for each of the one or more switching periods, sampling the sensed signal at the middle of the on-time period, and holding the sampled sensed signal representing the inductor current at the middle of the on-time period. For each of the one or more switching periods, the first signal represents a sum of a first multiplication result and a second multiplication result generated based on at least information associated with the held and sampled sensed signal, and the second signal represents the switching period multiplied by a predetermined current magnitude. The process for processing information associated with the first signal and the second signal includes integrating period-by-period differences between the first signal and the second signal for a plurality of switching periods, and the third signal represents the integrated period-by-period differences. The integrated period-by-period differences are smaller than a predetermined threshold in magnitude.
• Depending upon embodiment, one or more benefits may be achieved. These benefits and various additional objects, features and advantages of the present invention can be fully appreciated with reference to the detailed description and accompanying drawings that follow.
4. BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a simplified diagram showing a conventional LED lighting system with a Buck converter.
• FIG. 2 is a simplified diagram showing an operation mechanism for the lighting system that operates in the discontinuous conduction mode (DCM).
• FIG. 3 is a simplified diagram showing an LED lighting system according to one embodiment of the present invention.
• FIGS. 4(A), (B), and (C) are simplified diagrams showing timing diagrams for thelighting system300 that operates in the discontinuous conduction mode (DCM), the continuous conduction mode (CCM), and the critical conduction mode (CRM), respectively.
• FIG. 5 is a simplified diagram for a LED lighting system according to another embodiment of the present invention.
• FIG. 6 is a simplified diagram for a LED lighting system according to yet another embodiment of the present invention.
• FIG. 7 is a simplified diagram for a LED lighting system according to yet another embodiment of the present invention.
• FIG. 8 is a simplified diagram for a LED lighting system according to yet another embodiment of the present invention.
• FIG. 9 is a simplified diagram for a LED lighting system according to yet another embodiment of the present invention.
• FIG. 10 is a simplified diagram for a LED lighting system according to yet another embodiment of the present invention.
• FIG. 11 is a simplified diagram for a LED lighting system according to yet another embodiment of the present invention.
• FIG. 12 is a simplified diagram for a LED lighting system according to yet another embodiment of the present invention.
5. DETAILED DESCRIPTION OF THE INVENTION
• The present invention is directed to integrated circuits. More particularly, the invention provides lighting systems and methods for constant current control in various operation modes. Merely by way of example, the invention has been applied to one or more light emitting diodes. But it would be recognized that the invention has a much broader range of applicability.
• FIG. 2 is a simplified diagram showing an operation mechanism for thelighting system100 that operates in the discontinuous conduction mode (DCM). Thewaveform210 represents a voltage between the terminals122 and124 (e.g., V_DS) as a function of time, thewaveform220 represents a current flowing through the inductor140 (e.g. I_L) as a function of time, and thewaveform230 represents the current sensing signal114 (e.g., V_CS) as a function of time.
• For example, when thepower switch120 is turned on (e.g., during T_on), theinductor140 is magnetized and the current that flows through the inductor140 (e.g. I_L) flows through thepower switch120 and thesensing resistor160. Thesensing resistor160 converts the inductor current (e.g. I_L) into the current sensing signal114 (e.g., V_CS). In another example, when thepower switch120 is turned off (e.g., during T_off), theinductor140 is demagnetized and the inductor current (e.g. I_L) flows through thediode130, thecapacitor150, and the one ormore LEDs190. In yet another example, a lamp current192 (e.g., an output current) that flows through the one or more LEDs190 (e.g., I_LED) is equal to the average of the inductor current (e.g., the average of I_L). If the average of the inductor current is regulated to a predetermined level, the lamp current192 is also regulated to the predetermined level. Therefore, the lamp current192 can be estimated by sensing the inductor current (e.g. I_L) through thesensing resistor160 and calculating the on-time of the power switch120 (e.g., T_on).
• As discussed above, thelighting system100 attempts to control the lamp current192 by controlling the peak magnitude of the inductor current (e.g. I_L). The lamp current192 is equal to the average of the inductor current, but the relationship between the average of the inductor current and the peak magnitude of the inductor current depends on the input AC voltage (e.g., VAC). For example, if theconventional lighting system100 operates, with a fixed switching frequency, in the continuous conduction mode (CCM) or the discontinuous conduction mode (DCM), the on-time should decrease with increasing input AC voltage (e.g., VAC) in order to control the peak magnitude of the inductor current. As a result, the average of the inductor current and the lamp current192 also decrease with increasing input AC voltage. Therefore, the lamp current192 does not remain constant with respect to various input AC voltages.
• FIG. 3 is a simplified diagram showing an LED lighting system according to one embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. Thelighting system300 includes a pulse-width-modulation (PWM)controller310, aswitch320, adiode330, aninductor340,capacitors350 and352, asensing resistor360, and acapacitor364.
• For example, theswitch320, thediode330, theinductor340, thecapacitor350, and thesensing resistor360 are the same as thepower switch120, thediode130, theinductor140, thecapacitor150, and thesensing resistor160, respectively. In another example, theswitch320 is a MOS transistor. In yet another example, theswitch320 is a bipolar transistor (e.g. an NPN bipolar transistor). In yet another example, theswitch320 is an insulated gate bipolar transistor (IGBT).
• In one embodiment, thePWM controller310 includes a constant-current control component380, ademagnetization component382, an over-current-protection (OCP)component384, aclock generator386, areference signal generator388, alogic component362, a flip-flop component394, adrive component396, and a leading-edge-blankingcomponent308. In another embodiment, the PWM controller includesterminals372,374,376,378, and379.
• As shown inFIG. 3, thelighting system300 receives aninput voltage332 and provides a lamp current392 (e.g., an output current) and a lamp voltage to one ormore LEDs390. For example, thePWM controller310 outputs adrive signal312 through the terminal372 to theswitch320. In another example, thedrive signal312 corresponds to a switching period (e.g., T_S). According to one embodiment, if theswitch320 is turned on (e.g., during T_on), the current that flows through the inductor340 (e.g. I_L) is sensed by thesensing resistor360, and consequently, a current sensing signal314 (e.g., V_cs) is received by the over-current-protection (OCP)component384 through the terminal374 and the leading-edge-blankingcomponent308. For example, in response, the over-current-protection (OCP)component384 generates acontrol signal385.
• According to another embodiment, thedemagnetization component382 receives asignal354 through the terminal376 from thecapacitor352, and in response generates ademagnetization signal383. According to yet another embodiment, theclock generator386 generates aclock signal387, and thereference signal generator388 generates a reference voltage signal381 (e.g., V_REF) and a reference current signal389 (e.g., I_REF).
• In one embodiment, thedrive signal312, thecurrent sensing signal314, thedemagnetization signal383, theclock signal387, and the referencecurrent signal389 are received by the constant-current control component380 connected to the capacitor364 (e.g., through the terminal378). For example, in response, the constant-current control component380 outputs acontrol signal391 to thelogic component362. In another example, thelogic component362 receives the control signals391 and385 and outputs alogic signal393. In another embodiment, thelogic signal393 is received by the flip-flop component394, which also receives theclock signal387 and generates a modulation signal395. For example, the modulation signal395 is received by thedrive component396. In another example, thedrive component396 generate thedrive signal312 based on at least the modulation signal395.
• Thelighting system300 can regulate the lamp current392 that flows through the one or more LEDs390 (e.g., I_LED) in various operation modes, such as the discontinuous conduction mode (DCM), the continuous conduction mode (CCM), and/or the critical conduction mode (CRM), according to certain embodiments. For example, the lamp current392 is maintained at a constant level, regardless of the lamp voltage, the inductance of theinductor340, and/or theinput voltage332.
• FIGS. 4(A), (B), and (C) are simplified diagrams showing timing diagrams for thelighting system300 that operates in the discontinuous conduction mode (DCM), the continuous conduction mode (CCM), and the critical conduction mode (CRM), respectively.
• As shown inFIG. 4(A), in DCM, the off-time of theswitch320, T_off, is much longer than the demagnetization period, T_demag. The demagnetization process ends at point C, and the next switching cycle starts after the completion of the demagnetization process. The demagnetization period is determined as follows:
• $\begin{array}{cc}{T}_{\mathrm{demag}}=\frac{I_{\mathrm{L\_p}}}{\left(V_o/L\right)}=\frac{I_{\mathrm{L\_p}}\times L}{V_o}& \left(\mathrm{Equation}1\right)\end{array}$
• where V₀represents the lamp voltage across the one ormore LEDs390, I_{L_p}represents the peak magnitude of the inductor current (e.g., I_L) at the end of the on-time of theswitch320. Additionally, L represents the inductance of theinductor340. Moreover, as shown inFIG. 4(A), I_{L_0}represents the initial magnitude of the inductor current (e.g., I_L) at the beginning of the on-time of theswitch320, and is equal to zero.
• In DCM, the lamp current392, which is equal to the average inductor current, is as follows:
• $\begin{array}{cc}{I}_{\mathrm{out}}=\frac{1}{2}\times I_{\mathrm{L\_p}}\times \frac{T_{\mathrm{demag}}+T_{\mathrm{on}}}{T_s}& \left(\mathrm{Equation}2\right)\end{array}$
• where I_outrepresents the lamp current392, and T_onrepresents the on-time of theswitch320.
• As shown inFIG. 4(B), in CCM, the next switching cycle starts before the demagnetization process is completed. The off-time of theswitch320, T_off, is shorter than the demagnetization period, T_demag. In CCM, the lamp current392, which is equal to the average inductor current, is determined as follows:
• $\begin{array}{cc}{I}_{\mathrm{out}}=\frac{1}{2}\times \left(I_{\mathrm{L\_}0}+I_{L\mathrm{\_p}}\right)\times \frac{T_{\mathrm{off}}+T_{\mathrm{on}}}{T_s}=\frac{1}{2}\times \left(I_{L\_0}+I_{\mathrm{L\_p}}\right).& \left(\mathrm{Equation}3\right)\end{array}$
• As shown inFIG. 4(C), in CRM, the demagnetization period, T_demag, is slightly shorter than the off-time of the switch, T_off. The demagnetization process ends at point C, and the next switching cycle starts shortly after the completion of the demagnetization process. The next switching cycle starts at a minimum voltage level (e.g., a valley) of the drain voltage of a MOS transistor switch or at a minimum voltage level (e.g., a valley) of the collector voltage of a bipolar transistor switch.
• In CRM, the lamp current392, which is equal to the average inductor current, is determined as follows:
• $\begin{array}{cc}{I}_{\mathrm{out}}=\frac{1}{2}\times I_{\mathrm{L\_p}}\times \frac{T_{\mathrm{demag}}+T_{\mathrm{on}}}{T_s}.& \left(\mathrm{Equation}4\right)\end{array}$
• Since the demagnetization period, T_demag, is approximately equal to the off-time of theswitch320, T_off, and the initial magnitude of the inductor current (e.g., I_L) at the beginning of the on-time of theswitch320 is equal to zero,
• $\begin{array}{cc}{I}_{\mathrm{out}}\approx \frac{1}{2}\times I_{\mathrm{L\_p}}\times \frac{T_{\mathrm{off}}+T_{\mathrm{on}}}{T_s}=\frac{1}{2}\times I_{\mathrm{L\_p}}.& \left(\mathrm{Equation}5\right)\end{array}$
• Referring toFIG. 3, the lamp current392 is the averaged magnitude of the inductor current (e.g., I_L) in each switching cycle as follows:
• $\begin{array}{cc}{I}_{\mathrm{out}}=\frac{1}{T}\times {\int }_0^TI_L\left(t\right)t.& \left(\mathrm{Equation}6\right)\end{array}$
• where T represents an integration period, and I_Lrepresents the inductor current that flows through theinductor340. For example, T is equal to or larger than T_S, which represents the switching period.
• According to one embodiment, to achieve
• 
  I_out=I_C  (Equation 7)
• the following can be obtained with Equation 6:
• 
  ∫₀^T(t)dt=I_C×T=∫₀^TI_Cdt  (Equation 8)
• where I_crepresents a constant current magnitude.
• In another embodiment, in practice, if
• 
  |∫₀^TI_L(t)dt−∫₀^TI_Cdt|≦C  (Equation 9)
• where C is a predetermined threshold, then the constant lamp current392 can be achieved or substantially achieved.
• Referring toFIGS. 4(A), (B), and (C), as discussed above, the lamp current392 is determined according toEquation 2,Equation 3, andEquation 4, for DCM, CCM and CRM, respectively. Additionally, for CCM and CRM,
• $\begin{array}{cc}{I}_{\mathrm{out}}=\frac{1}{T_s}\times {\int }_0^{T_s}I_L\left(t\right)t=\frac{1}{T_{\mathrm{on}}}\times {\int }_0^{T_{\mathrm{on}}}I_L\left(t\right)t.& \left(\mathrm{Equation}10\right)\end{array}$
• Also referring toFIG. 3, the inductor current I_Lduring the on-time of theswitch320 as shown in Equation 10 is converted by thesensing resistor360 into thecurrent sensing signal314, which is received by thePWM controller310 through the terminal374.
• According to another embodiment, for DCM, CCM and CRM,
• 
  (I_{L_p}(i)+_{L_0}(i))×(T_demag(i)₊T_on(i))=I_C(i)×T_s(i)  (Equation 11A)
• 
  or(2×I_{L_Ton/2}(i))×(T_demag(i)+T_on(i))=I_C(i)×T_s(i)  (Equation 11B)
• where i corresponds to the i^thswitching cycle. Additionally, I_{L_Ton/2}represents the magnitude of the inductor current (e.g., I_L) at the middle of the on-time of theswitch320.
• Also, since in CCM, the next switching cycle starts before the demagnetization process is completed, the actual length of the demagnetization process before the next switching cycle starts is limited to the off-time of the switch; hence T_offcan be represented by T_demagin CCM.
• For example, if
• $\begin{array}{cc}{\mathrm{Limit}}_{N\to \infty }\hspace{1em}\left|\left(\sum _{i=0}^N\left(I_{L_{—}p}\left(i\right)+I_{L_{—}0}\left(i\right)\right)\times \left(T_{\mathrm{demag}}\left(i\right)+T_{\mathrm{on}}\left(i\right)\right)-\sum _{i=0}^NI_c\left(i\right)\times T_s\left(i\right)\right)\right|<C& \left(\mathrm{Equation}12A\right)\\ \mathrm{or}{\mathrm{Limit}}_{N\to \infty }\hspace{1em}\left|\left(\sum _{i=0}^N\left(2\times I_{L_{—}\mathrm{Ton}\text{/}2}\left(i\right)\right)\times \left(T_{\mathrm{demag}}\left(i\right)+T_{\mathrm{on}}\left(i\right)\right)-\sum _{i=0}^NI_c\left(i\right)\times T_s\left(i\right)\right)\right|<C& \left(\mathrm{Equation}12B\right)\end{array}$
• where C is a predetermined threshold, then the constant lamp current can be achieved.
• In another example, Equation 12A is rewritten into an integration format as follows:
• 
  |∫[I_{L_p}(i)+I_{L_0}(i)]×[U(t−T_s(i))−U(t−T_s(i)−T_demag(i))]dt−∫I_C(t)dt|  (Equation 13)
• where U(t) is the unit step function, and I_C(t) is equal to a constant I_{C_ref}. Hence, in the steady state, the following can be obtained:
• 
  |∫[I_{L_p}(i)+I_{L_0}(i)]×[U(t−T_s(i))−U(t−T_s(i)−T_demag(i))]dt−∫I_{C_ref}dt|  (Equation 14A)
• In yet another example, Equation 12B can be rewritten into an integration format, and hence, in the steady state, the following can be obtained:
• 
  |∫[2×I_{L_Ton/2}]×[U(t−T_s(i))−U(t−T_s(i)−T_demag(i))]dt−∫I_{C_ref}dt|≦C  (Equation 14B)
• In one embodiment, referring toEquations 2, 3 and 4, for DCM, CCM and CRM,
• $\begin{array}{cc}{I}_{\mathrm{out}}=\frac{1}{2}\times \left(I_{L_{—}0}+I_{L_{—}p}\right)\times \frac{T_{\mathrm{demag}}+T_{\mathrm{on}}}{T_s}& \left(\mathrm{Equation}15\right)\end{array}$
• where T_demagrepresents T_offfor CCM, and I_{L_0}is equal to zero for DCM and CRM.
• For example, if the lamp current392 is maintained at a constant level, e.g.,
• $\begin{array}{cc}{I}_{\mathrm{out}}=\frac{1}{2}\times I_{\mathrm{ref}}& \left(\mathrm{Equation}16\right)\\ \mathrm{then}\left(I_{L_{—}p}+I_{L_{—}0}\right)\times \frac{T_{\mathrm{demag}}+T_{\mathrm{on}}}{T_s}=I_{\mathrm{ref}}& \left(\mathrm{Equation}17\right)\end{array}$
• where I_refrepresents a constant current level. Hence,
• 
  (I_{L_p}+I_{L_0})×(T_demag+T_on)=I_ref×T_s  (Equation 18).
• In another example, T_s, T_demag, and T_onmay vary from one switching cycle to another switching cycle, so for the ith switching cycle, the following may be obtained:
• 
  (I_{L_p}(i)+I_{L_0}(i))×(T_demag(i)+T_on(i))≠I_ref×T_s(i)  (Equation 19)
• But if
• $\begin{array}{cc}{\mathrm{Limit}}_{N\to \infty }\hspace{1em}\left|\left(\sum _{i=0}^N\left(I_{L_{—}p}\left(i\right)+I_{L_{—}0}\left(i\right)\right)\times \left(T_{\mathrm{demag}}\left(i\right)+T_{\mathrm{on}}\left(i\right)\right)-\sum _{i=0}^NI_{\mathrm{ref}}\times T_s\left(i\right)\right)\right|<A& \left(\mathrm{Equation}20A\right)\end{array}$
• where A represents a predetermined threshold, the following integration format can be obtained:
• 
  |∫(I_{L_p}(i)+I_{L_0}(i))×[U(t−T_s(i))−U(t−T_s(i)−T_on(i)−T_demag(i))]dt−∫I_refdt|≦A  (Equation 21A)
• where U(t) is the unit step function.
• In yet another example, if
• $\begin{array}{cc}{\mathrm{Limit}}_{N\to \infty }\hspace{1em}\left|\left(\sum _{i=0}^N\left(2\times I_{L_{—}\mathrm{Ton}\text{/}2}\left(i\right)\right)\times \left(T_{\mathrm{demag}}\left(i\right)+T_{\mathrm{on}}\left(i\right)\right)-\sum _{i=0}^NI_{\mathrm{ref}}\times T_s\left(i\right)\right)\right|<A& \left(\mathrm{Equation}20B\right)\end{array}$
• where A represents a predetermined threshold, the following integration format can be obtained:
• 
  |∫(x×I_{L_Ton/2}(i))×[U(t−T_s(i))−U(t−T_s(i)−T_on(i)−T_demag(i))]dt−∫I_refdt|≦A  (Equation 21B)
• where U(t) is the unit step function.
• According to yet another embodiment, if Equations 20A and 21A are satisfied and/or Equations 20B and 21B are satisfied, the lamp current392 is maintained at a constant level, regardless of the lamp voltage, the inductance of theinductor340, and/or theinput voltage332.
• For example, referring toFIG. 3, when theswitch320 is turned on (e.g., during T_on), the current that flows through the inductor340 (e.g. I_L) is sensed by thesensing resistor360, which generates the current sensing signal314 (e.g., V_cs) as follows:
• 
  V_cs=I_L×R_s  (Equation 22)
• where V_csrepresents thecurrent sensing signal314, I_Lrepresents the current that flows through theinductor340, and R_Srepresents the resistance of thesensing resistor360.
• In another example, based on Equations 21(A) and22, one can obtain the following:
• $\begin{array}{cc}|\frac{1}{R_s}\int \left(V_{{\mathrm{cs}}_{—}p}\left(i\right)+I_{{\mathrm{cs}}_{—}0}\left(i\right)\right)\times \hspace{1em}\left[U\left(t-T_s\left(i\right)\right)-U\left(t-T_s\left(i\right)-T_{\mathrm{on}}\left(i\right)-T_{\mathrm{demag}}\left(i\right)\right)\right]t-\int I_{\mathrm{ref}}t|<A& \left(\mathrm{Equation}23A\right)\end{array}$
• where V_{cs_p}represents the peak magnitude of thecurrent sensing signal314, and corresponds to the peak magnitude of the inductor current at the end of the on-time of theswitch320. Additionally, V_{cs_0}represents the initial magnitude of thecurrent sensing signal314, and corresponds to the initial magnitude of the inductor current at the beginning of the on-time of theswitch320.
• In yet another example, based on Equations 21(B) and 22, one can obtain the following:
• $\begin{array}{cc}|\frac{1}{R_s}\int \left(2\times V_{{\mathrm{cs}}_{—}\mathrm{Ton}\text{/}2}\left(i\right)\right)\times \hspace{1em}\left[U\left(t-T_s\left(i\right)\right)-U\left(t-T_s\left(i\right)-T_{\mathrm{on}}\left(i\right)-T_{\mathrm{demag}}\left(i\right)\right)\right]t-\int I_{\mathrm{ref}}t|<A& \left(\mathrm{Equation}23B\right)\end{array}$
• where V_{cs_Ton/2}represents the magnitude of thecurrent sensing signal314 at the middle of the on-time of theswitch320.
• As discussed above and further emphasized here,FIG. 3 is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. For example,FIG. 3 is implemented according toFIG. 5,FIG. 6,FIG. 7,FIG. 8,FIG. 9,FIG. 10,FIG. 11, and/orFIG. 12. In another example, the leading-edge-blankingcomponent308 is removed, and the current sensing signal314 (e.g., V_cs) is received by the over-current-protection (OCP)component384 through the terminal374 without going through the leading-edge-blankingcomponent308.
• FIG. 5 is a simplified diagram for a LED lighting system according to another embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. Thelighting system500 includes a switch420, adiode430, aninductor440,capacitors450 and452, and asensing resistor460. Additionally, thelighting system500 also includes cycle-by-cycle processing components520 and522, acapacitor530, asignal conditioning component532, atransconductance amplifier540, acomparator542, ademagnetization detection component544, a leading-edge blanking component550, a flip-flop component554, aclock generator556, and adriver component558.
• For example, the switch420, thediode430, theinductor440, thecapacitor450, and thesensing resistor460 are the same as thepower switch120, thediode130, theinductor140, thecapacitor150, and thesensing resistor160, respectively. In another example, the cycle-by-cycle processing components520 and522, thesignal conditioning component532, thetransconductance amplifier540, thecomparator542, thedemagnetization detection component544, the leading-edge blanking component550, the flip-flop component554, theclock generator556, and thedriver component558 are located on achip510. In yet another example, thecapacitor530 is located off thechip510. In yet another example, thechip510 includesterminals512,514,516,518, and519.
• As shown inFIG. 5, thelighting system500 receives aninput voltage534 and provides a lamp current592 (e.g., an output current) and a lamp voltage to one or more LEDs590. According to one embodiment, during the on-time of the switch420 (e.g., T_on), a current that flows through theinductor440 and the switch420 is sensed by theresistor460. For example, theresistor460 generates, through the terminal514 and with the leading-edge blanking component550, acurrent sensing signal552. In another example, during the on-time of the switch420 (e.g., T_on), thecurrent sensing signal552 is as follows:
• 
  V_cs=I_L×R_s  (Equation 24)
• where V_csrepresents thecurrent sensing signal552, I_Lrepresents the current that flows through theinductor440, and R_srepresents the resistance of theresistor460.
• In yet another example, combining Equations 20A and 24, the following is obtained:
• $\begin{array}{cc}{\mathrm{Limit}}_{N\to \infty }\hspace{1em}\left|\left(\frac{1}{R_s}\sum _{i=0}^N\left(V_{{\mathrm{cs}}_{—}p}\left(i\right)+V_{{\mathrm{cs}}_{—}0}\left(i\right)\right)\times \left(T_{\mathrm{demag}}\left(i\right)+T_{\mathrm{on}}\left(i\right)\right)-\sum _{i=0}^NI_{\mathrm{ref}}\times T_s\left(i\right)\right)\right|<A& \left(\mathrm{Equation}25A\right)\end{array}$
• where A represents a predetermined threshold, and I_refrepresents a predetermined referenced current. Additionally, V_{cs_p}represents the peak magnitude of thecurrent sensing signal552, which, for example, corresponds to the peak magnitude of the inductor current at the end of the on-time of the switch420. Moreover, V_{cs_0}represents the initial magnitude of thecurrent sensing signal552, which, for example, corresponds to the initial magnitude of the inductor current at the beginning of the on-time of the switch420. Also, T_srepresents the switching period of the switch420, and T_onrepresents the on-time of the switch420. Additionally, T_demagrepresents the demagnetization period for DCM and CRM, and T_demagrepresents the off-time of the switch420 (e.g., T_off) for CCM.
• In yet another example, combining Equations 20B and 24, the following is obtained:
• $\begin{array}{cc}{\mathrm{Limit}}_{N\to \infty }\hspace{1em}\left|\left(\frac{1}{R_s}\sum _{i=0}^N\left(2\times V_{{\mathrm{cs}}_{—}\mathrm{Ton}\text{/}2}\left(i\right)\right)\times \left(T_{\mathrm{demag}}\left(i\right)+T_{\mathrm{on}}\left(i\right)\right)-\sum _{i=0}^NI_{\mathrm{ref}}\times T_s\left(i\right)\right)\right|<A& \left(\mathrm{Equation}25B\right)\end{array}$
• where A represents a predetermined threshold, and I_refrepresents a predetermined referenced current. Additionally, V_{cs_Ton/2}represents the magnitude of thecurrent sensing signal552 at the middle of the on-time of the switch420. Also, T_srepresents the switching period of the switch420, and T_onrepresents the on-time of the switch420. Additionally, T_demagrepresents the demagnetization period for DCM and CRM, and T_demagrepresents the off-time of the switch420 (e.g., T_off) for CCM.
• According to some embodiments, thecurrent sensing signal552 is received by the cycle-by-cycle processing component520. In one embodiment, for each switching cycle, theprocessing component520 generates asignal521 that is equal to (I_{L_p}+I_{L_0})×(T_on+T_demag). In another embodiment, for each switching cycle, theprocessing component520 generates asignal521 that is equal to (I_{L_p}+I_{L_0})λ (T_on)+(2×I_{L_Ton/2})×(T_demag).
• For example, for each switching cycle, the average inductor current during the on-time of the switch420 (e.g., T_on) is determined directly based on the sensed current552 as ½ (I_{L_p}+I_{L_0}) when the switch420 is closed. In another example, for each switching cycle, the average inductor current during the demagnetization period (e.g., T_demag) is determined indirectly based on the sensed current552 at the middle of the on-time as I_{L_Ton/2}, which is sampled when the switch420 is closed and then held by the cycle-by-cycle processing component520. In yet another example, for each switching cycle, the average inductor current during the off-time (e.g., T_off) is determined indirectly based on the sensed current552 at the middle of the on-time as (I_{L_Ton/2})×(T_demag)/(T_off), and I_{L_Ton/2}is sampled when the switch420 is closed and then held by the cycle-by-cycle processing component520. For DCM and CRM, the demagnetization period (e.g., T_demag) represents duration of the demagnetization process, but for CCM, the demagnetization period (e.g., T_demag) represents duration of the off-time according to certain embodiments.
• In yet another example, for each switching cycle, theprocessing component522 generates asignal523 that is equal to I_ref×T_s. In yet another example, thedemagnetization detection component544 receives afeedback signal564 from thecapacitor452, and generates aDemag signal545. The Demag signal545 has a pulse width of T_demagfor each switching cycle.
• According to another embodiment, thesignals523 and521 are received by thetransconductance amplifier540. For example, the magnitude difference of I_ref×T_s−(I_{L_p}+I_{L_0})×(T_on+T_demag) is amplified and integrated by thetransconductance amplifier540 and thecapacitor530 as part of the practical implementation of Equation 25A. In another example, the magnitude difference of I_ref×T_s−└(I_{L_p}+I_{L_0})_x(T_on)+(2×I_{L_Ton/2})×(T_demag)┘ is amplified and integrated by thetransconductance amplifier540 and thecapacitor530 as part of the practical implementation of Equation 25B. In another example, thetransconductance amplifier540 and thecapacitor530 form an integrator, which generates asignal531 that is received by thecomparator542 directly or indirectly through thesignal conditioning component532.
• According to yet another embodiment, thecomparator542 also receives thecurrent sensing signal552, and in response generates acomparison signal543. For example, thecomparison signal543 is received by the flip-flop component554, and the flip-flop component554 also receives aclock signal555 from theclock generator556 and generates amodulation signal557. In another example, themodulation signal557 is received by thedriver component558, which in response generates thedrive signal559.
• In one embodiment, thedrive signal559 is sent to the switch420 through the terminal512, and is also received by the cycle-by-cycle processing component520. In another embodiment, thesignal531 is used to adjust the pulse width of thedrive signal559 with pulse-width modulation.
• As discussed above and further emphasized here,FIG. 5 is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. For example, thesignal conditioning component532 is removed, and thesignal531 is received directly by thecomparator542. In another example, the leading-edge blanking component550 is removed, and thesignal552 is received directly from the terminal514. In yet another example, thecapacitor530 is located on thechip510. In yet another example, for CRM, theclock generator556 is replaced by a pulse signal generator, which receives the Demag signal545 and in response generates pulses of apulse signal555. In yet another example, thepulse signal555 is received by the flip-flop component554, and different pulses of thepulse signal555 correspond to different switching cycles.
• FIG. 6 is a simplified diagram for a LED lighting system according to yet another embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. Thelighting system600 includes aswitch4620, adiode4630, aninductor4640,capacitors4650 and4652, and asensing resistor4660. Additionally, thelighting system600 also includes acomparator642, ademagnetization detection component644, a leading-edge blanking component650, a flip-flop component654, aclock generator656, and adriver component658. Moreover, thelighting system600 also includes sampling-and-holdingcomponents662 and664, voltage-to-current converters660,666 and668, aswitch680, and acapacitor690. Also, thelighting system600 further includes asignal amplifier686, a voltage-to-current converter688, and aswitch682.
• For example, theswitch4620, thediode4630, theinductor4640, thecapacitor4650, and thesensing resistor4660 are the same as thepower switch120, thediode130, theinductor140, thecapacitor150, and thesensing resistor160, respectively. In another example, thecomparator642, thedemagnetization detection component644, the leading-edge blanking component650, the flip-flop component654, theclock generator656, thedriver component658, the sampling-and-holdingcomponents662 and664, the voltage-to-current converters660,666 and668, theswitch680, thesignal amplifier686, the voltage-to-current converter688, and theswitch682 are located on achip610. In yet another example, thecapacitor690 is located off thechip610. In yet another example, thechip610 includesterminals612,614,616,618, and619.
• According to one embodiment, in CCM, the next switching cycle starts before the demagnetization process is completed. For example, the actual length of the demagnetization process (e.g., T_demag) before the next switching cycle starts is limited to the off-time of the switch4620 (e.g., T_off); hence T_offcan be represented by T_demagin CCM. According to another embodiment, in DCM, the off-time of the switch4620 (e.g., T_off) is much longer than the demagnetization period (e.g., T_demag). According to yet another embodiment, in CRM, the off-time of the switch4620 (e.g., T_off) is slightly longer than the demagnetization period (e.g., T_demag).
• As shown inFIG. 6, thelighting system600 receives aninput voltage632 and provides a lamp current692 (e.g., an output current) and a lamp voltage to one ormore LEDs4690. In one embodiment, a current that flows through theinductor4640 is sensed by theresistor4660. For example, theresistor4660 generates, through the terminal614 and with the leading-edge blanking component650, acurrent sensing signal652.
• In another embodiment, the sampling-and-holdingcomponent662 receives at least adrive signal659 and acontrol signal661. For example, thecontrol signal661 includes, for each switching cycle, a pulse that has a rising edge at the beginning of the on-time of the switch4620 (e.g., at the rising edge of the drive signal659). In another example, during the pulse, the current sensing signal652 (e.g., V_cs) is sampled and held as a voltage signal663 (e.g., V_s2). In yet another example, after the falling edge of the pulse, thevoltage signal663 remains constant (e.g., being equal to V_{cs_0}) until the next pulse of thecontrol signal661. In one embodiment, the pulse of thecontrol signal661 is so narrow that V_{cs_0}equals approximately and thus represents thecurrent sensing signal652 at the beginning of the on-time of theswitch4620.
• In yet another embodiment, the sampling-and-holdingcomponent664 receives at least thedrive signal659, which includes, for each switching cycle, a pulse that has a width corresponding to the on-time of the switch4620 (e.g., T_on). For example, during the pulse of thedrive signal659, the current sensing signal652 (e.g., V_cs) is sampled and held as a voltage signal665 (e.g., V_s3). In another example, after the falling edge of the pulse, thevoltage signal665 remains constant (e.g., being equal to V_{cs_p}) until the next pulse of thedrive signal659.
• As shown inFIG. 6, the voltage signals663 and665 are received by the voltage-to-current converters666 and668, which in response generatecurrent signals667 and669, respectively, according to one embodiment. For example, thecurrent signal667 is represented by I_s2, and thecurrent signal669 is represented by I_s3. In another example, the sum of thecurrent signals667 and669 forms a sinking current681 (e.g., I_sink2), which is used to discharge thecapacitor690 if theswitch680 is closed.
• According to another embodiment, theswitch680 is controlled by aDemag signal645, which is generated by thedemagnetization detection component644. For example, if the Demag signal645 is at the logic high level, theswitch680 is closed. In another example, theswitch680 is closed during the demagnetization period and is open during the rest of the switching period. In yet another example, the sinking current681 discharges thecapacitor690 during the demagnetization period (e.g., during T_demag).
• Also, as shown inFIG. 6, thesignal amplifier686 receives the current sensing signal652 (e.g., V_cs) and generates a voltage signal687 (e.g., V_s1) according to one embodiment. For example, the voltage signal687 (e.g., V_s1) equals two times the current sensing signal652 (e.g., V_cs) in magnitude. According to another embodiment, thevoltage signal687 is received by the voltage-to-current converter688, which in response generates a sinking current689 (e.g., I_sink1). For example, the sinking current689 is used to discharge thecapacitor690 if theswitch682 is closed.
• According to yet another embodiment, theswitch682 is controlled by asignal685, which has been generated based on thesignal659. For example, if thesignal685 is at the logic high level, theswitch682 is closed, and if thesignal685 is at the logic low level, theswitch682 is open. In another example, theswitch682 is closed during the on-time of theswitch4620, and is open during the off-time of theswitch4620. In yet another example, the sinking current689 discharges thecapacitor690 during the on-time of theswitch4620. According to yet another embodiment, the voltage-to-current converter660 receives a predetermined voltage signal691 (e.g., V_ref), and in response generates a charging current661 (e.g., I_ref). For example, the charging current661 charges thecapacitor690 during the switching period (e.g., during TO. According to yet another embodiment, the signal683 (e.g., V_C) is generated by the charging current661 (e.g., I_ref), the discharging current681 (e.g., I_sink2), and the discharging current689 (e.g., I_sink1) for thecapacitor690. For example, the signal683 (e.g., V_C) decreases in magnitude during the demagnetization period (e.g., during T_demag), and increases during the rest of the switching cycle.
• In one embodiment, thecomparator642 receives the signal683 (e.g., V_C) and also receives thecurrent sensing signal652 through theslope compensation component684. For example, in response, thecomparator642 generates acomparison signal643, which is received by the flip-flop component654. In another example, the flip-flop component654 also receives aclock signal655 from theclock generator656 and generates amodulation signal657. In yet another example, themodulation signal657 is received by thedriver component658, which in response outputs thedrive signal659 to theswitch4620 and the sampling-and-holdingcomponents662 and664.
• According to one embodiment, for CCM, DCM and CRM,
• 
  I_s2=α×V_{cs_0}=α×I_{L_0}×R_s  (Equation 26)
• 
  andI_s3=α×V_{cs_p}=α×I_{L_p}×R_s  (Equation 27).
• 
  HenceI_sink2=I_s2+I_s3=α×I_{L_0}×R_s+α×I_{L_p}×R_s  (Equation 28).
• 
  Additionally,I_sink1=2×α×V_cs  (Equation 29)
• where α is a constant related to the voltage-to-current converters666,668 and688, and R_sis the resistance of thesensing resistor4660.
• According to another embodiment, if, within each switching cycle, the charging and the discharging of thecapacitor690 are equal, thelighting system600 reaches the equilibrium (e.g., the steady state), as follows:
• 
  I_ref×T_s=½×I_{sink1_p}×T_on+I_sink2×T_demag  (Equation 30)
• 
  whereI_{sink1_p}=2×α×V_{cs_p}  (Equation 31).
• Combining Equations 28-31, the following can be obtained:
• $\begin{array}{cc}{I}_{\mathrm{ref}}=\alpha \times R_s\times \left(I_{L_{—}0}+I_{L_{—}p}\right)\times \frac{\left(T_{\mathrm{on}}+T_{\mathrm{demag}}\right)}{T_s}.& \left(\mathrm{Equation}32A\right)\\ \mathrm{If}I_{\mathrm{ref}}=\beta \times V_{\mathrm{ref}}& \left(\mathrm{Equation}33A\right)\\ \left(I_{L_{—}0}+I_{L_{-}p}\right)\times \frac{\left(T_{\mathrm{on}}+T_{\mathrm{demag}}\right)}{T_s}=\frac{\beta \times V_{\mathrm{ref}}}{\alpha \times R_s}& \left(\mathrm{Equation}34A\right)\end{array}$
• where β is a constant related to the voltage-to-current converter660.
• $\begin{array}{cc}\mathrm{Since}I_{\mathrm{out}}=\frac{1}{2}\times \left(I_{L_{—}0}+I_{L_{—}p}\right)\times \frac{T_{\mathrm{demag}}+T_{\mathrm{on}}}{T_s}& \left(\mathrm{Equation}35A\right)\\ \mathrm{then}I_{\mathrm{out}}=\frac{\mathrm{<figure-callout\; label="\beta "\; filenames="US20160278178A1-20160922-D00008.png,US20160278178A1-20160922-D00009.png"\; state="\{\{state\}\}">\beta </figure-callout>}}{2\times \alpha \times R_s}\times V_{\mathrm{ref}}& \left(\mathrm{Equation}36A\right)\end{array}$
• where I_outrepresents the lamp current692. According to yet another embodiment, α, β, R_s, and V_refare all constants, so the constant lamp current692 is achieved.
• As discussed above and further emphasized here,FIG. 6 is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. In one embodiment, the leading-edge blanking component650 is removed, and thesignal652 is received directly from the terminal614. In another embodiment, thecapacitor690 is located on thechip610. In yet another embodiment, a low-pass filter and/or a buffer are added to process thesignal683 before thesignal683 is received by thecomparator642. For example, a voltage divider (e.g., formed by two resistors) is further added to divide the processedsignal683 before the processedsignal683 is received by thecomparator642.
• According to another embodiment, for DCM and CRM, V_{cs_0}is equal to zero, so the sampling-and-holdingcomponent662 and the voltage-to-current converter666 are removed if thelighting system600 does not need to operate in CCM for constant lamp current692. According to yet another embodiment, for CRM, theclock generator656 is replaced by a pulse signal generator, which receives the Demag signal645 and in response generates pulses of apulse signal655. For example, thepulse signal655 is received by the flip-flop component654, and different pulses of thepulse signal655 correspond to different switching cycles.
• According to yet another embodiment, thelighting system600 is modified so that the following can be obtained:
• $\begin{array}{cc}{I}_{\mathrm{ref}}=\alpha \times R_s\times \left(2\times I_{L_{—}\mathrm{Ton}\text{/}2}\right)\times \frac{\left(T_{\mathrm{on}}+T_{\mathrm{demag}}\right)}{T_s}.& \left(\mathrm{Equation}32B\right)\\ \mathrm{If}I_{\mathrm{ref}}=\beta \times V_{\mathrm{ref}}& \left(\mathrm{Equation}33B\right)\\ \left(2\times I_{L_{—}\mathrm{Ton}\text{/}2}\right)\times \frac{\left(T_{\mathrm{on}}+T_{\mathrm{demag}}\right)}{T_s}=\frac{\beta \times V_{\mathrm{ref}}}{\alpha \times R_s}& \left(\mathrm{Equation}34B\right)\end{array}$
• where β is a constant related to the voltage-to-current converter660.
• $\begin{array}{cc}\mathrm{Since}I_{\mathrm{out}}=\frac{1}{2}\times \left(I_{L_{—}\mathrm{Ton}\text{/}2}\right)\times \frac{T_{\mathrm{demag}}+T_{\mathrm{on}}}{T_s}& \left(\mathrm{Equation}35B\right)\\ \mathrm{then}I_{\mathrm{out}}=\frac{\mathrm{<figure-callout\; label="\beta "\; filenames="US20160278178A1-20160922-D00008.png,US20160278178A1-20160922-D00009.png"\; state="\{\{state\}\}">\beta </figure-callout>}}{2\times \alpha \times R_s}\times V_{\mathrm{ref}}& \left(\mathrm{Equation}36B\right)\end{array}$
• where I_outrepresents the lamp current692. α, β, R_s, and V_refare all constants, so the constant lamp current692 is achieved according to certain embodiments.
• FIG. 7 is a simplified diagram for a LED lighting system according to yet another embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. Thelighting system700 includes aswitch4720, adiode4730, aninductor4740, acapacitor4750, and asensing resistor4760. Additionally, thelighting system700 also includes acomparator742, a leading-edge blanking component750, a flip-flop component754, aclock generator756, and adriver component758. Moreover, thelighting system700 also includes voltage-to-current converters760 and788,switches780 and782, acapacitor790, and asignal amplifier786.
• For example, theswitch4720, thediode4730, theinductor4740, thecapacitor4750, and thesensing resistor4760 are the same as thepower switch120, thediode130, theinductor140, thecapacitor150, and thesensing resistor160, respectively. In another example, thecomparator742, the leading-edge blanking component750, the flip-flop component754, theclock generator756, thedriver component758, the voltage-to-current converters760 and788, theswitches780 and782, and thesignal amplifier786 are located on achip710. In yet another example, thecapacitor790 is located off thechip710. In yet another example, thechip710 includesterminals712,714,718, and719.
• As shown inFIG. 7, thelighting system700 receives an input voltage732 and provides a lamp current792 (e.g., an output current) and a lamp voltage to one ormore LEDs4790. In one embodiment, a current that flows through theinductor4740 is sensed by theresistor4760. For example, theresistor4760 generates, through the terminal714 and with the leading-edge blanking component750, acurrent sensing signal752.
• In another embodiment, thesignal amplifier786 receives the current sensing signal752 (e.g., V_cs) and generates a voltage signal787 (e.g., V_s1). For example, the voltage signal787 (e.g., V_s1) equals two times the current sensing signal752 (e.g., V_cs) in magnitude. In yet another embodiment, the gain of thesignal amplifier786 is G (e.g. G being a predetermined positive number). In yet another embodiment, thevoltage signal787 is received by the voltage-to-current converter788, which in response generates a sinking current789 (e.g., I_sink1). For example, the sinking current789 is used to discharge thecapacitor790 if theswitch782 is closed. In another example, theswitch782 is controlled by asignal785, which has been generated based on adrive signal759.
• In yet another embodiment, the voltage-to-current converter760 receives a predetermined voltage signal791 (e.g., V_ref), and in response generates a charging current761 (e.g., I_ref). For example, the charging current761 is used to charge thecapacitor790 if theswitch780 is closed. In another example, theswitch780 is controlled by thesignal785, which has been generated based on thedrive signal759.
• According to one embodiment, if thesignal785 is at the logic high level, theswitches780 and782 are closed, and if thesignal785 is at the logic low level, theswitches780 and782 are open. For example, theswitches780 and782 are closed during the on-time of theswitch4720, and are open during the off-time of theswitch4720. In another example, the sinking current789 discharges thecapacitor790 and the charging current761 charges thecapacitor790 during the on-time of theswitch4720. According to another embodiment, the signal783 (e.g., V_C) is generated by the charging current761 (e.g., I_ref) and the discharging current789 (e.g., I_sink1) for thecapacitor790.
• As shown inFIG. 7, thecomparator742 receives the signal783 (e.g., V_C) and also receives thecurrent sensing signal752 through theslope compensation component784. For example, in response, thecomparator742 generates acomparison signal743, which is received by the flip-flop component754. In another example, the flip-flop component754 also receives aclock signal755 from theclock generator756 and generates amodulation signal757. In yet another example, themodulation signal757 is received by thedriver component758, which in response outputs thedrive signal759 to theswitch4720.
• According to one embodiment, for CCM, since
• $\begin{array}{cc}{I}_{\mathrm{out}}=\frac{1}{T_s}\times {\int }_0^{T_s}I_L\left(t\right)t=\frac{1}{T_{\mathrm{on}}}\times {\int }_0^{T_{\mathrm{on}}}I_L\left(t\right)t& \left(\mathrm{Equation}37\right)\\ \mathrm{then}I_{\mathrm{out}}=\frac{V_{\mathrm{ref}}}{R_s}& \left(\mathrm{Equation}38\right)\end{array}$
• where I_outrepresents the lamp current792 and R_sis the resistance of thesensing resistor4760. According to another embodiment, R_sand V_refare all constants, so the constant lamp current792 is achieved.
• As discussed above and further emphasized here,FIG. 7 is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. For example, the leading-edge blanking component750 is removed, and thesignal752 is received directly from the terminal714. In another example, thecapacitor790 is located on thechip710. In yet another example, a low-pass filter and/or a buffer are added to process thesignal783 before thesignal783 is received by thecomparator742. In yet another example, two resistors are further added to divide the processedsignal783 before the processedsignal783 is received by thecomparator742.
• FIG. 8 is a simplified diagram for a LED lighting system according to yet another embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. Thelighting system800 includes aswitch4820, adiode4830, aninductor4840, acapacitor4850, and asensing resistor4860. Additionally, thelighting system800 also includes acomparator842, a leading-edge blanking component850, a flip-flop component854, aclock generator856, and adriver component858. Moreover, thelighting system800 also includes atransconductance amplifier886,switches880 and882, and acapacitor890.
• For example, theswitch4820, thediode4830, theinductor4840, thecapacitor4850, and thesensing resistor4860 are the same as thepower switch120, thediode130, theinductor140, thecapacitor150, and thesensing resistor160, respectively. In another example, thecomparator842, the leading-edge blanking component850, the flip-flop component854, theclock generator856, thedriver component858, thetransconductance amplifier886, and theswitches880 and882 are located on achip810. In yet another example, thecapacitor890 is located off thechip810. In yet another example, thechip810 includesterminals812,814,818, and819.
• As shown inFIG. 8, thelighting system800 receives aninput voltage832 and provides a lamp current892 (e.g., an output current) and a lamp voltage to one ormore LEDs4890. In one embodiment, a current that flows through theinductor4840 is sensed by theresistor4860. For example, theresistor4860 generates, through the terminal814 and with the leading-edge blanking component850, acurrent sensing signal852.
• In another embodiment, thetransconductance amplifier886 receives the current sensing signal852 (e.g., V_cs), and also receives a predetermined voltage signal891 (e.g., V_ref) through theswitch880. For example, theswitch880 is controlled by asignal885, which has been generated based on adrive signal859. In another example, if thesignal885 is at the logic high level, theswitch880 is closed, and if thesignal885 is at the logic low level, theswitch880 is open. In yet another example, theswitch880 is closed during the on-time of theswitch4820, and is open during the off-time of theswitch4820.
• In yet another embodiment, during the on-time of theswitch4820, thetransconductance amplifier886 compares the current sensing signal852 (e.g., V_cs) and the predetermined voltage signal891 (e.g., V_ref), and converts the difference between the current sensing signal852 (e.g., V_cs) and the predetermined voltage signal891 (e.g., V_ref) into a current889. For example, the current889 is proportional to the difference between the current sensing signal852 (e.g., V_cs) and the predetermined voltage signal891 (e.g., V_ref). In another example, during the on-time of theswitch4820, the current889 charges thecapacitor890 if the predetermined voltage signal891 (e.g., V_ref) is larger than the current sensing signal852 (e.g., V_cs) in magnitude, and discharges thecapacitor890 if the predetermined voltage signal891 (e.g., V_ref) is smaller than the current sensing signal852 (e.g., V_cs) in magnitude.
• In yet another embodiment, during the off-time of theswitch4820, the predetermined voltage signal891 (e.g., V_ref) is shorted to the ground through theswitch882. For example, theswitch882 is controlled by asignal845, which has been generated based on thedrive signal859. In another example, if thesignal845 is at the logic high level, theswitch882 is closed, and if thesignal845 is at the logic low level, theswitch882 is open. In yet another example, theswitch882 is closed during the off-time of theswitch4820, and is open during the on-time of theswitch4820.
• As shown inFIG. 8, a signal883 (e.g., V_C) is generated by the current889 charging and/or discharging thecapacitor890. In one embodiment, thecomparator842 receives the signal883 (e.g., V_C) and also receives thecurrent sensing signal852 through theslope compensation component884. For example, in response, thecomparator842 generates acomparison signal843, which is received by the flip-flop component854. In another example, the flip-flop component854 also receives aclock signal855 from theclock generator856 and generates amodulation signal857. In yet another example, themodulation signal857 is received by thedriver component858, which in response outputs thedrive signal859 to theswitch4820.
• As discussed above and further emphasized here,FIG. 8 is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. For example, the leading-edge blanking component850 is removed, and thesignal852 is received directly from the terminal814. In another example, thecapacitor890 is located on thechip810.
• FIG. 9 is a simplified diagram for a LED lighting system according to yet another embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. Thelighting system900 includes a switch4920, adiode4930, aninductor4940,capacitors4950 and4952, and asensing resistor4960. Additionally, thelighting system900 also includes acomparator942, ademagnetization detection component944, a leading-edge blanking component950, a flip-flop component954, apulse signal generator956, and adriver component958. Moreover, thelighting system900 also includes atransconductance amplifier986,switches980 and982, and acapacitor990.
• For example, the switch4920, thediode4930, theinductor4940, thecapacitor4950, and thesensing resistor4960 are the same as thepower switch120, thediode130, theinductor140, thecapacitor150, and thesensing resistor160, respectively. In another example, thecomparator942, thedemagnetization detection component944, the leading-edge blanking component950, the flip-flop component954, thepulse signal generator956, thedriver component958, thetransconductance amplifier986, and theswitches980 and982 are located on achip910. In yet another example, thecapacitor990 is located off thechip910. In yet another example, thechip910 includesterminals912,914,916,918, and919.
• As shown inFIG. 9, thelighting system900 receives aninput voltage932 and provides a lamp current992 (e.g., an output current) and a lamp voltage to one ormore LEDs4990. In one embodiment, a current that flows through theinductor4940 is sensed by theresistor4960. For example, theresistor4960 generates, through the terminal914 and with the leading-edge blanking component950, acurrent sensing signal952.
• In another embodiment, thetransconductance amplifier986 receives the current sensing signal952 (e.g., V_cs), and also receives a predetermined voltage signal991 (e.g., V_ref) through theswitch980. For example, theswitch980 is controlled by asignal985, which has been generated based on adrive signal959. In another example, if thesignal985 is at the logic high level, theswitch980 is closed, and if thesignal985 is at the logic low level, theswitch980 is open. In yet another example, theswitch980 is closed during the on-time of the switch4920, and is open during the off-time of the switch4920.
• In yet another embodiment, during the on-time of the switch4920, thetransconductance amplifier986 compares the current sensing signal952 (e.g., V_cs) and the predetermined voltage signal991 (e.g., V_ref), and converts the difference between the current sensing signal952 (e.g., V_cs) and the predetermined voltage signal991 (e.g., V_ref) into a current989. For example, the current989 is proportional to the difference between the current sensing signal952 (e.g., V_cs) and the predetermined voltage signal991 (e.g., V_ref). In another example, during the on-time of the switch4920, the current989 charges thecapacitor990 if the predetermined voltage signal991 (e.g., V_ref) is larger than the current sensing signal952 (e.g., V_cs) in magnitude, and discharges thecapacitor990 if the predetermined voltage signal991 (e.g., V_ref) is smaller than the current sensing signal952 (e.g., V_cs) in magnitude.
• In yet another embodiment, during the off-time of the switch4920, the predetermined voltage signal991 (e.g., V_ref) is shorted to the ground through theswitch982. For example, theswitch982 is controlled by asignal945, which has been generated based on thedrive signal959. In another example, if thesignal945 is at the logic high level, theswitch982 is closed, and if thesignal945 is at the logic low level, theswitch982 is open. In yet another example, theswitch982 is closed during the off-time of the switch4920, and is open during the on-time of the switch4920.
• As shown inFIG. 9, a signal983 (e.g., V_C) is generated by the current989 charging and/or discharging thecapacitor990. In one embodiment, thecomparator942 receives the signal983 (e.g., V_C) and also receives thecurrent sensing signal952. For example, in response, thecomparator942 generates acomparison signal943, which is received by the flip-flop component954. In another example, the flip-flop component954 also receives apulse signal955 from thepulse signal generator956 and generates amodulation signal957. In yet another example, themodulation signal957 is received by thedriver component958, which in response outputs thedrive signal959 to the switch4920. In another embodiment, thepulse signal generator956 receives a Demag signal945 from thedemagnetization detection component944, and in response generates pulses of thepulse signal955. For example, different pulses of thepulse signal955 correspond to different switching cycles.
• As discussed above and further emphasized here,FIG. 9 is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. For example, the leading-edge blanking component950 is removed, and thesignal952 is received directly from the terminal914. In another example, thecapacitor990 is located on thechip910. In yet another example, a slope compensation component is added, through which thecomparator942 receives thecurrent sensing signal952.
• FIG. 10 is a simplified diagram for a LED lighting system according to yet another embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. Thelighting system1000 includes aswitch5020, adiode5030, aninductor5040,capacitors5050 and5052, and asensing resistor5060. Additionally, thelighting system1000 also includes acomparator1042, ademagnetization detection component1044, a leading-edge blanking component1050, a flip-flop component1054, aclock generator1056, and adriver component1058. Moreover, thelighting system1000 also includes sampling-and-holdingcomponents1062 and1064, voltage-to-current converters1060,1066 and1068, aswitch1080, and acapacitor1090. Also, thelighting system1000 further includes asignal amplifier1086, a voltage-to-current converter1088, aswitch1082, amultiplier component1096, andresistors1098 and1099.
• For example, theswitch5020, thediode5030, theinductor5040, thecapacitor5050, and thesensing resistor5060 are the same as thepower switch120, thediode130, theinductor140, thecapacitor150, and thesensing resistor160, respectively. In another example, thecomparator1042, thedemagnetization detection component1044, the leading-edge blanking component1050, the flip-flop component1054, theclock generator1056, thedriver component1058, the sampling-and-holdingcomponents1062 and1064, the voltage-to-current converters1060,1066 and1068, theswitch1080, thesignal amplifier1086, the voltage-to-current converter1088, theswitch1082, and themultiplier component1096 are located on achip1010. In yet another example, thecapacitor1090 is located off thechip1010. In yet another example, thechip1010 includesterminals1012,1014,1016,1017,1018, and1019.
• According to one embodiment, in CCM, the next switching cycle starts before the demagnetization process is completed. For example, the actual length of the demagnetization process (e.g., T_demag) before the next switching cycle starts is limited to the off-time of the switch5020 (e.g., T_off); hence T_offcan be represented by T_demagin CCM. According to another embodiment, in DCM, the off-time of the switch5020 (e.g., T_off) is much longer than the demagnetization period (e.g., T_demag). According to yet another embodiment, in CRM, the off-time of the switch5020 (e.g., T_off) is slightly longer than the demagnetization period (e.g., T_demag).
• As shown inFIG. 10, thelighting system1000 receives aninput voltage1032 and provides a rectifiedvoltage1093 and a lamp current1092 (e.g., an output current) to drive one ormore LEDs5090. In one embodiment, a current that flows through theinductor5040 is sensed by theresistor5060. For example, theresistor5060 generates, through the terminal1014 and with the leading-edge blanking component1050, acurrent sensing signal1052.
• In another embodiment, the sampling-and-holdingcomponent1062 receives at least adrive signal1059 and acontrol signal1061. For example, thecontrol signal1061 includes, for each switching cycle, a pulse that has a rising edge at the beginning of the on-time of the switch5020 (e.g., at the rising edge of the drive signal1059). In another example, during the pulse, the current sensing signal1052 (e.g., V_cs) is sampled and held as a voltage signal1063 (e.g., V_s2). In yet another example, after the falling edge of the pulse, thevoltage signal1063 remains constant (e.g., being equal to V_cs) until the next pulse of thecontrol signal1061. In one embodiment, the pulse of thecontrol signal1061 is so narrow that V_{cs_0}equals approximately and thus represents thecurrent sensing signal1052 at the beginning of the on-time of theswitch5020.
• In yet another embodiment, the sampling-and-holdingcomponent1064 receives at least thedrive signal1059, which includes, for each switching cycle, a pulse that has a width corresponding to the on-time of the switch5020 (e.g., T_on). For example, during the pulse of thedrive signal1059, the current sensing signal1052 (e.g., V_cs) is sampled and held as a voltage signal1065 (e.g., V_s3). In another example, after the falling edge of the pulse, thevoltage signal1065 remains constant (e.g., being equal to V_{cs_p}) until the next pulse of thedrive signal1059.
• As shown inFIG. 10, thevoltage signals1063 and1065 are received by the voltage-to-current converters1066 and1068, which in response generatecurrent signals1067 and1069, respectively, according to one embodiment. For example, thecurrent signal1067 is represented by I_s2, and thecurrent signal1069 is represented by I_s3. In another example, the sum of thecurrent signals1067 and1069 forms a sinking current1081 (e.g., I_sink2), which is used to discharge thecapacitor1090 if theswitch1080 is closed.
• According to another embodiment, theswitch1080 is controlled by aDemag signal1045, which is generated by thedemagnetization detection component1044. For example, if theDemag signal1045 is at the logic high level, theswitch1080 is closed. In another example, theswitch1080 is closed during the demagnetization period and is open during the rest of the switching period. In yet another example, the sinking current1081 discharges thecapacitor1090 during the demagnetization period (e.g., during T_demag).
• Also, as shown inFIG. 10, thesignal amplifier1086 receives the current sensing signal1052 (e.g., V_cs) and generates a voltage signal1087 (e.g., V_s1) according to one embodiment. For example, the voltage signal1087 (e.g., V_s1) equals two times the current sensing signal1052 (e.g., V_cs) in magnitude. According to another embodiment, thevoltage signal1087 is received by the voltage-to-current converter1088, which in response generates a sinking current1089 (e.g., I_sink1). For example, the sinking current1089 is used to discharge thecapacitor1090 if theswitch1082 is closed.
• According to yet another embodiment, theswitch1082 is controlled by asignal1085, which has been generated based on thesignal1059. For example, if thesignal1085 is at the logic high level, theswitch1082 is closed, and if thesignal1085 is at the logic low level, theswitch1082 is open. In another example, theswitch1082 is closed during the on-time of theswitch5020, and is open during the off-time of theswitch5020. In yet another example, the sinking current1089 discharges thecapacitor1090 during the on-time of theswitch5020. According to yet another embodiment, the voltage-to-current converter1060 receives a predetermined voltage signal1091 (e.g., V_ref), and in response generates a charging current1061 (e.g., I_ref). For example, the charging current1061 charges thecapacitor1090 during the switching period (e.g., during T_s). According to yet another embodiment, the signal1083 (e.g., V_C) is generated by the charging current1061 (e.g., I_ref), the discharging current1081 (e.g., I_sink2), and the discharging current1089 (e.g., I_sink1) for thecapacitor1090. For example, the signal1083 (e.g., V_C) decreases in magnitude during the demagnetization period (e.g., during T_demag), and increases during the rest of the switching cycle.
• As shown inFIG. 10, theresistor1098 receives the rectifiedvoltage1093, and together with theresistor1099, generates a signal1095. For example, the signal1095 is received by themultiplier component1096 through theterminal1017. In another example, themultiplier component1096 also receives the signal1083 (e.g., V_C) and generates acontrol signal1097 based on at least information associated with thesignals1095 and1083.
• In one embodiment, thecomparator1042 receives thecontrol signal1097, and also receives thecurrent sensing signal1052 through theslope compensation component1084. For example, in response, thecomparator1042 generates acomparison signal1043, which is received by the flip-flop component1054. In another example, the flip-flop component1054 also receives aclock signal1055 from theclock generator1056 and generates amodulation signal1057. In yet another example, themodulation signal1057 is received by thedriver component1058, which in response outputs thedrive signal1059 to theswitch5020 and the sampling-and-holdingcomponents1062 and1064. In another embodiment, for DCM, CCM and CRM, thelighting system1000 has power factor that is equal to or larger than 0.9, such as being equal to 1. For example, the high power factor and precise control of constant lamp current1092 are simultaneously achieved by thelighting system1000.
• In yet another embodiment, if, over a plurality of switching cycles, the charging and the discharging of thecapacitor1090 are equal, thelighting system1000 reaches the equilibrium (e.g., the steady state), as follows:
• $\begin{array}{cc}\sum _{i=0}^NI_{\mathrm{ref}}\times T_s\left(i\right)=\sum _{i=0}^N\frac{1}{2}\times I_{\sin k1_{—}p}\left(i\right)\times T_{\mathrm{on}}\left(i\right)+I_{\sin k2}\left(i\right)\times T_{\mathrm{demag}}\left(i\right)& \left(\mathrm{Equation}39\right)\end{array}$
• where i represents the ith switching cycle.
• As discussed above and further emphasized here,FIG. 10 is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. For example, the leading-edge blanking component1050 is removed, and thesignal1052 is received directly from the terminal1014. In another example, thecapacitor1090 is located on thechip1010. In yet another example, a low-pass filter and/or a buffer are added to process thesignal1083 before thesignal1083 is received by themultiplier component1096. In yet another example, two resistors are further added to divide the processedsignal1083 before the processedsignal1083 is received by themultiplier component1096.
• In yet another example, for DCM and CRM, V_{cs_0}is equal to zero, so the sampling-and-holdingcomponent1062 and the voltage-to-current converter1066 are removed if thelighting system1000 does not need to operate in DCM and CRM for constant lamp current1092. In yet another example, for CRM, theclock generator1056 is replaced by a pulse signal generator, which receives theDemag signal1045 and in response generates pulses of apulse signal1055. In yet another example, thepulse signal1055 is received by the flip-flop component1054, and different pulses of thepulse signal1055 correspond to different switching cycles.
• FIG. 11 is a simplified diagram for a LED lighting system according to yet another embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. Thelighting system1100 includes a switch5120, adiode5130, aninductor5140,capacitors5150 and5152, and asensing resistor5160. Additionally, thelighting system1100 also includes acomparator1142, ademagnetization detection component1144, a leading-edge blanking component1150, a flip-flop component1154, apulse signal generator1156, and adriver component1158. Moreover, thelighting system1100 also includes atransconductance amplifier1186, switches1180 and1182, acapacitor1190, and a rampingsignal generator1199.
• For example, the switch5120, thediode5130, theinductor5140, thecapacitor5150, and thesensing resistor5160 are the same as thepower switch120, thediode130, theinductor140, thecapacitor150, and thesensing resistor160, respectively. In another example, thecomparator1142, thedemagnetization detection component1144, the leading-edge blanking component1150, the flip-flop component1154, thepulse signal generator1156, thedriver component1158, thetransconductance amplifier1186, theswitches1180 and1182, and the rampingsignal generator1199 are located on achip1110. In yet another example, thecapacitor1190 is located off thechip1110. In yet another example, thechip1110 includesterminals1112,1114,1116,1118, and1119.
• As shown inFIG. 11, thelighting system1100 receives aninput voltage1132 and provides a lamp current1192 (e.g., an output current) and a lamp voltage to one ormore LEDs5190. In one embodiment, a current that flows through theinductor5140 is sensed by theresistor5160. For example, theresistor5160 generates, through the terminal1114 and with the leading-edge blanking component1150, acurrent sensing signal1152.
• In another embodiment, thetransconductance amplifier1186 receives the current sensing signal1152 (e.g., V_cs), and also receives a predetermined voltage signal1191 (e.g., V_ref) through theswitch1180. For example, theswitch1180 is controlled by asignal1185, which has been generated based on adrive signal1159. In another example, if thesignal1185 is at the logic high level, theswitch1180 is closed, and if thesignal1185 is at the logic low level, theswitch1180 is open. In yet another example, theswitch1180 is closed during the on-time of the switch5120, and is open during the off-time of the switch5120.
• In yet another embodiment, during the on-time of the switch5120, thetransconductance amplifier1186 compares the current sensing signal1152 (e.g., V_cs) and the predetermined voltage signal1191 (e.g., V_ref), and converts the difference between the current sensing signal1152 (e.g., V_cs) and the predetermined voltage signal1191 (e.g., V_ref) into a current1189. For example, the current1189 is proportional to the difference between the current sensing signal1152 (e.g., V_cs) and the predetermined voltage signal1191 (e.g., V_ref). In another example, during the on-time of the switch5120, the current1189 charges thecapacitor1190 if the predetermined voltage signal1191 (e.g., \T_ref) is larger than the current sensing signal1152 (e.g., V_cs) in magnitude, and discharges thecapacitor1190 if the predetermined voltage signal1191 (e.g., V_ref) is smaller than the current sensing signal1152 (e.g., V_cs) in magnitude.
• In yet another embodiment, during the off-time of the switch5120, the predetermined voltage signal1191 (e.g., V_ref) is shorted to the ground through theswitch1182. For example, theswitch1182 is controlled by asignal1145, which has been generated based on thedrive signal1159. In another example, if thesignal1145 is at the logic high level, theswitch1182 is closed, and if thesignal1145 is at the logic low level, theswitch1182 is open. In yet another example, theswitch1182 is closed during the off-time of the switch5120, and is open during the on-time of the switch5120.
• As shown inFIG. 11, a signal1183 (e.g., V_C) is generated by the current1189 charging and/or discharging thecapacitor1190. In one embodiment, thecomparator1142 receives the signal1183 (e.g., V_C) and also receives a ramping signal1193. For example, the ramping signal1193 is generated by the rampingsignal generator1199 in response to apulse signal1155. In another example, in response, thecomparator1142 generates acomparison signal1143, which is received by the flip-flop component1154. In another example, the flip-flop component1154 also receives thepulse signal1155 from thepulse signal generator1156 and generates amodulation signal1157. In yet another example, themodulation signal1157 is received by thedriver component1158, which in response outputs thedrive signal1159 to the switch5120. In another embodiment, thepulse signal generator1156 receives aDemag signal1145 from thedemagnetization detection component1144, and in response generates pulses of thepulse signal1155. For example, different pulses of thepulse signal1155 correspond to different switching cycles.
• As discussed above and further emphasized here,FIG. 11 is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. For example, the leading-edge blanking component1150 is removed, and thesignal1152 is received directly from the terminal1114. In another example, thecapacitor1190 is located on thechip1110.
• FIG. 12 is a simplified diagram for a LED lighting system according to yet another embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. Thelighting system1200 includes aswitch5220, adiode5230, aninductor5240,capacitors5250 and5252, and asensing resistor5260. Additionally, thelighting system1200 also includes acomparator1242, ademagnetization detection component1244, a leading-edge blanking component1250, a flip-flop component1254, apulse signal generator1256, and adriver component1258. Moreover, thelighting system1200 also includes atransconductance amplifier1286, switches1280 and1282, acapacitor1290, amultiplier component1296, andresistors1298 and1299.
• For example, theswitch5220, thediode5230, theinductor5240, thecapacitor5250, and thesensing resistor5260 are the same as thepower switch120, thediode130, theinductor140, thecapacitor150, and thesensing resistor160, respectively. In another example, thecomparator1242, thedemagnetization detection component1244, the leading-edge blanking component1250, the flip-flop component1254, thepulse signal generator1256, thedriver component1258, thetransconductance amplifier1286, theswitches1280 and1282, and themultiplier component1296 are located on achip1210. In yet another example, thecapacitor1290 is located off thechip1210. In yet another example, thechip1210 includesterminals1212,1214,1216,1217,1218, and1219.
• As shown inFIG. 12, thelighting system1200 receives aninput voltage1232 and provides a rectifiedvoltage1293 and a lamp current1292 (e.g., an output current) to drive one ormore LEDs5290. In one embodiment, a current that flows through theinductor5240 is sensed by theresistor5260. For example, theresistor5260 generates, through the terminal1214 and with the leading-edge blanking component1250, acurrent sensing signal1252.
• In another embodiment, thetransconductance amplifier1286 receives the current sensing signal1252 (e.g., V_cs), and also receives a predetermined voltage signal1291 (e.g., V_ref) through theswitch1280. For example, theswitch1280 is controlled by asignal1285, which has been generated based on adrive signal1259. In another example, if thesignal1285 is at the logic high level, theswitch1280 is closed, and if thesignal1285 is at the logic low level, theswitch1280 is open. In yet another example, theswitch1280 is closed during the on-time of theswitch5220, and is open during the off-time of theswitch5220.
• In yet another embodiment, during the on-time of theswitch5220, thetransconductance amplifier1286 compares the current sensing signal1252 (e.g., V_cs) and the predetermined voltage signal1291 (e.g., V_ref), and converts the difference between the current sensing signal1252 (e.g., V_cs) and the predetermined voltage signal1291 (e.g., V_ref) into a current1289. For example, the current1289 is proportional to the difference between the current sensing signal1252 (e.g., V_cs) and the predetermined voltage signal1291 (e.g., V_ref). In another example, during the on-time of theswitch5220, the current1289 charges thecapacitor1290 if the predetermined voltage signal1291 (e.g., V_ref) is larger than the current sensing signal1252 (e.g., V_cs) in magnitude, and discharges thecapacitor1290 if the predetermined voltage signal1291 (e.g., V_ref) is smaller than the current sensing signal1252 (e.g., V_cs) in magnitude.
• In yet another embodiment, during the off-time of theswitch5220, the predetermined voltage signal1291 (e.g., V_ref) is shorted to the ground through theswitch1282. For example, theswitch1282 is controlled by asignal1245, which has been generated based on thedrive signal1259. In another example, if thesignal1245 is at the logic high level, theswitch1282 is closed, and if thesignal1245 is at the logic low level, theswitch1282 is open. In yet another example, theswitch1282 is closed during the off-time of theswitch5220, and is open during the on-time of theswitch5220.
• As shown inFIG. 12, a signal1283 (e.g., V_C) is generated by the current1289 charging and/or discharging thecapacitor1290. In one embodiment, theresistor1298 receives the rectifiedvoltage1293, and together with theresistor1299, generates asignal1295. For example, thesignal1295 is received by themultiplier component1296 through theterminal1217. In another example, themultiplier component1296 also receives the signal1283 (e.g., V_C) and generates acontrol signal1297 based on at least information associated with thesignals1295 and1283.
• In another embodiment, thecomparator1242 receives thecontrol signal1297, and also receives thecurrent sensing signal1252. For example, in response, thecomparator1242 generates acomparison signal1243, which is received by the flip-flop component1254. In another example, the flip-flop component1254 also receives apulse signal1255 from thepulse signal generator1256 and generates amodulation signal1257. In yet another example, themodulation signal1257 is received by thedriver component1258, which in response outputs thedrive signal1259 to theswitch5220. In yet another embodiment, thepulse signal generator1256 receives aDemag signal1245 from thedemagnetization detection component1244, and in response generates pulses of thepulse signal1255. For example, different pulses of thepulse signal1255 correspond to different switching cycles.
• As discussed above and further emphasized here,FIG. 12 is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. For example, the leading-edge blanking component1250 is removed, and thesignal1252 is received directly from theterminal1214. In another example, thecapacitor1290 is located on thechip1210. In yet another example, a slope compensation component is added, through which thecomparator1242 receives thecurrent sensing signal1252.
• For example, some or all components of various embodiments of the present invention each are, individually and/or in combination with at least another component, implemented using one or more software components, one or more hardware components, and/or one or more combinations of software and hardware components. In another example, some or all components of various embodiments of the present invention each are, individually and/or in combination with at least another component, implemented in one or more circuits, such as one or more analog circuits and/or one or more digital circuits. In yet another example, various embodiments and/or examples of the present invention can be combined. In yet another example, various embodiments and/or examples of the present invention are combined so that a lighting system can provide constant lamp current in various operation modes, such as in all of the DCM mode, the CCM mode and the CRM mode under certain conditions (e.g., with different input voltages).
• The present invention has a wide range of applications. Certain embodiments of the present invention can be used to drive one or more light emitting diodes with high power factor and precise control of constant lamp current.
• According to another embodiment, a system (e.g., as implemented according toFIG. 3) for providing at least an output current to one or more light emitting diodes includes a control component (e.g., the component380) configured to receive at least a demagnetization signal (e.g., the signal383), a sensed signal (e.g., the signal314) and a reference signal (e.g., the signal389) and to generate a control signal (e.g., the signal391) based on at least information associated with the demagnetization signal, the sensed signal and the reference signal, and a logic and driving component (e.g., thecomponents362,394 and396) configured to receive at least the control signal (e.g., the signal391) and output a drive signal (e.g., the signal312) to a switch (e.g., the component320) based on at least information associated with the control signal (e.g., the signal391). The switch (e.g., the component320) is connected to a first diode terminal of a diode (e.g., the component330) and a first inductor terminal of an inductor (e.g., the component340). The diode further includes a second diode terminal, and the inductor further includes a second inductor terminal. The second diode terminal and the second inductor terminal are configured to provide at least the output current to the one or more light emitting diodes. The control signal (e.g., the signal391) is configured to regulate the output current at a constant magnitude.
• According to yet another embodiment, a method (e.g., as implemented according toFIG. 3) for providing at least an output current to one or more light emitting diodes includes receiving at least a demagnetization signal (e.g., the signal383), a sensed signal (e.g., the signal314) and a reference signal (e.g., the signal389), processing information associated with the demagnetization signal, the sensed signal and the reference signal, and generating a control signal (e.g., the signal391) based on at least information associated with the demagnetization signal, the sensed signal and the reference signal. Additionally, the method includes receiving at least the control signal (e.g., the signal391), processing information associated with the control signal, and outputting a drive signal (e.g., the signal312) to a switch (e.g., the component320) connected to a first diode terminal of a diode (e.g., the component330) and a first inductor terminal of an inductor (e.g., the component340). The diode further includes a second diode terminal, and the inductor further includes a second inductor terminal. The second diode terminal and the second inductor terminal are configured to provide at least the output current to the one or more light emitting diodes. Moreover, the method includes regulating the output current at a predetermined magnitude based on at least information associated with the control signal (e.g., the signal391).
• According to yet another embodiment, a system (e.g., as implemented according toFIG. 5) for providing at least an output current to one or more light emitting diodes includes a first signal processing component (e.g., the component520) configured to receive at least a sensed signal (e.g., the signal552) and generate a first signal (e.g., the signal521). The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the system includes a second signal processing component (e.g., the component522) configured to generate a second signal (e.g., the signal523), an integrator component (e.g., thecomponents530 and540) configured to receive the first signal and the second signal and generate a third signal (e.g., the signal531), and a comparator (e.g., the component542) configured to process information associated with the third signal and the sensed signal and generate a comparison signal (e.g., the signal543) based on at least information associated with the third signal and the sensed signal. Moreover, the system includes a signal generator (e.g., the component554) configured to receive at least the comparison signal and generate a modulation signal (e.g., the signal557), and a gate driver (e.g., the component558) configured to receive the modulation signal (e.g., the signal557) and output a drive signal to the switch. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period for the switch and a demagnetization period for a demagnetization process. For each of the one or more switching periods, the first signal represents a multiplication result of a first sum of the on-time period and the demagnetization period and a second sum of a first current magnitude and a second current magnitude, and the second signal represents the switching period multiplied by a predetermined current magnitude. The first current magnitude represents the inductor current at the beginning of the on-time period, and the second current magnitude represents the inductor current at the end of the on-time period. The integrator component is further configured to integrate period-by-period differences between the first signal and the second signal for a plurality of switching periods, and the third signal (e.g., the signal531) represents the integrated period-by-period differences. The integrated period-by-period differences are smaller than a predetermined threshold in magnitude.
• According to yet another embodiment, a method (e.g., as implemented according toFIG. 5) for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the method includes processing information associated with the sensed signal, generating a first signal based on at least information associated with the sensed signal, generating a second signal, receiving the first signal and the second signal, processing information associated with the first signal and the second signal, and generating a third signal based on at least information associated with the first signal and the second signal. Moreover, the method includes processing information associated with the third signal and the sensed signal, generating a comparison signal based on at least information associated with the third signal and the sensed signal, receiving at least the comparison signal, generating a modulation signal based on at least information associated with the comparison signal, receiving the modulation signal, and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period and a demagnetization period. For each of the one or more switching periods, the first signal represents a multiplication result of a first sum of the on-time period and the demagnetization period and a second sum of a first current magnitude and a second current magnitude, and the second signal represents the switching period multiplied by a predetermined current magnitude. The first current magnitude represents the inductor current at the beginning of the on-time period, and the second current magnitude represents the inductor current at the end of the on-time period. The process for processing information associated with the first signal and the second signal includes integrating period-by-period differences between the first signal and the second signal for a plurality of switching periods, and the third signal represents the integrated period-by-period differences. The integrated period-by-period differences are smaller than a predetermined threshold in magnitude.
• According to yet another embodiment, a system (e.g., as implemented according toFIG. 5) for providing at least an output current to one or more light emitting diodes includes a first signal processing component (e.g., the component520) configured to receive at least a sensed signal (e.g., the signal552) and generate a first signal (e.g., the signal521). The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the system includes a second signal processing component (e.g., the component522) configured to generate a second signal (e.g., the signal523), an integrator component (e.g., thecomponents530 and540) configured to receive the first signal and the second signal and generate a third signal (e.g., the signal531), and a comparator (e.g., the component542) configured to process information associated with the third signal and the sensed signal and generate a comparison signal (e.g., the signal543) based on at least information associated with the third signal and the sensed signal. Moreover, the system includes a signal generator (e.g., the component554) configured to receive at least the comparison signal and generate a modulation signal (e.g., the signal557), and a gate driver (e.g., the component558) configured to receive the modulation signal (e.g., the signal557) and output a drive signal to the switch. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period for the switch and a demagnetization period for a demagnetization process. For each of the one or more switching periods, the first signal represents a sum of a first multiplication result and a second multiplication result, and the second signal represents the switching period multiplied by a predetermined current magnitude. The first multiplication result is equal to the on-time period multiplied by a sum of a first current magnitude and a second current magnitude. The first current magnitude represents the inductor current at the beginning of the on-time period, and the second current magnitude represents the inductor current at the end of the on-time period. The second multiplication result is equal to two multiplied by the demagnetization period and further multiplied by a third current magnitude, and the third current magnitude represents the inductor current at the middle of the on-time period. The integrator component is further configured to integrate period-by-period differences between the first signal and the second signal for a plurality of switching periods, and the third signal (e.g., the signal531) represents the integrated period-by-period differences. The integrated period-by-period differences are smaller than a predetermined threshold in magnitude.
• According to yet another embodiment, a method (e.g., as implemented according toFIG. 5) for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the method includes processing information associated with the sensed signal, generating a first signal based on at least information associated with the sensed signal, generating a second signal, receiving the first signal and the second signal, processing information associated with the first signal and the second signal, and generating a third signal based on at least information associated with the first signal and the second signal. Moreover, the method includes processing information associated with the third signal and the sensed signal, generating a comparison signal based on at least information associated with the third signal and the sensed signal, receiving at least the comparison signal, and generating a modulation signal based on at least information associated with the comparison signal. Also, the method includes receiving the modulation signal, and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period and a demagnetization period. For each of the one or more switching periods, the first signal represents a sum of a first multiplication result and a second multiplication result, and the second signal represents the switching period multiplied by a predetermined current magnitude. The first multiplication result is equal to the on-time period multiplied by a sum of a first current magnitude and a second current magnitude. The first current magnitude represents the inductor current at the beginning of the on-time period, and the second current magnitude represents the inductor current at the end of the on-time period. The second multiplication result is equal to two multiplied by the demagnetization period and further multiplied by a third current magnitude, and the third current magnitude represents the inductor current at the middle of the on-time period. The process for processing information associated with the first signal and the second signal includes integrating period-by-period differences between the first signal and the second signal for a plurality of switching periods, and the third signal represents the integrated period-by-period differences. The integrated period-by-period differences are smaller than a predetermined threshold in magnitude.
• According to yet another embodiment, a system (e.g., as implemented according toFIG. 6) for providing at least an output current to one or more light emitting diodes includes a first sampling-and-holding and voltage-to-current-conversion component (e.g., thecomponents662 and666) configured to receive at least a sensed signal and generate a first current signal (e.g., the signal667). The sensed signal is associated with an inductor current flowing through an inductor coupled to a first switch. Additionally, the system includes a second sampling-and-holding and voltage-to-current-conversion component (e.g., thecomponents664 and668) configured to receive at least the sensed signal and generate a second current signal (e.g., the signal669), and a signal-amplification and voltage-to-current-conversion component (e.g., thecomponents686 and688) configured to receive at least the sensed signal and generate a third current signal (e.g., the signal689). Moreover, the system includes a current-signal generator configured to generate a fourth current signal (e.g., the signal661), and a capacitor coupled to the current-signal generator, coupled through a second switch to the first sampling-and-holding and voltage-to-current-conversion component and the second sampling-and-holding and voltage-to-current-conversion component, and coupled through a third switch to the signal-amplification and voltage-to-current-conversion component. The capacitor is configured to generate a voltage signal. Also, the system includes a comparator (e.g., the component642) configured to process information associated with the voltage signal (e.g., the signal683) and the sensed signal (e.g., the signal652) and generate a comparison signal (e.g., the signal643) based on at least information associated with the voltage signal and the sensed signal. Additionally, the system includes a modulation-signal generator (e.g., the component654) configured to receive at least the comparison signal and generate a modulation signal (e.g., the signal657), and a gate driver configured to receive the modulation signal and output a drive signal to the first switch. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period for the first switch and a demagnetization period for a demagnetization process. The first current signal represents the inductor current at the beginning of the on-time period, the second current signal represents the inductor current at the end of the on-time period, and the third current signal represents the inductor current. For each of the one or more switching periods, the first current signal and the second current signal are configured to discharge or charge the capacitor during only the demagnetization period, the third current signal is configured to discharge or charge the capacitor during only the on-time period, and the fourth current signal is configured to charge or discharge the capacitor during the switching period.
• According to yet another embodiment, a method (e.g., as implemented according toFIG. 6) for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch, processing information associated with the sensed signal, and generating a first current signal, a second current signal, and a third current signal based on at least information associated with the sensed signal. Additionally, the method includes generating a fourth current signal, processing information associated with the first current signal, the second current signal, the third current signal, and the fourth current signal, and generating a voltage signal, by at least a capacitor, based on at least information associated with the first current signal, the second current signal, the third current signal, and the fourth current signal. Moreover, the method includes processing information associated with the voltage signal and the sensed signal, generating a comparison signal based on at least information associated with the voltage signal and the sensed signal, receiving at least the comparison signal, and generating a modulation signal based on at least information associated with the comparison signal. Also, the method includes receiving the modulation signal, and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period and a demagnetization period. The first current signal represents the inductor current at the beginning of the on-time period, the second current signal represents the inductor current at the end of the on-time period, and the third current signal represents the inductor current. For each of the one or more switching periods, the process for processing information associated with the first current signal, the second current signal, the third current signal, and the fourth current signal includes discharging or charging the capacitor with the first current signal and the second current signal during only the demagnetization period, discharging or charging the capacitor with the third current signal during only the on-time period, and charging or discharging the capacitor with the fourth current signal during the switching period.
• According to yet another embodiment, a system (e.g., as implemented according toFIG. 7) for providing at least an output current to one or more light emitting diodes includes a signal-amplification and voltage-to-current-conversion component (e.g., thecomponents786 and788) configured to receive at least a sensed signal (e.g., the signal752) and generate a first current signal (e.g., the signal789). The sensed signal is associated with an inductor current flowing through an inductor coupled to a first switch. Additionally, the system includes a current-signal generator configured to generate a second current signal (e.g., the signal761), and a capacitor coupled to the current-signal generator, and coupled through a second switch to the signal-amplification and voltage-to-current-conversion component. The capacitor is configured to generate a voltage signal. Moreover, the system includes a comparator configured to process information associated with the voltage signal and the sensed signal and generate a comparison signal based on at least information associated with the voltage signal and the sensed signal, a modulation-signal generator (e.g., the component754) configured to receive at least the comparison signal and generate a modulation signal (e.g., the signal757), and a gate driver configured to receive the modulation signal and output a drive signal to the first switch. The drive signal is associated with at least one or more switching periods, and the first current signal represents the inductor current. Each of the one or more switching periods includes at least an on-time period for the first switch. For each of the one or more switching periods, the first current signal is configured to discharge or charge the capacitor during only the on-time period, and the second current signal is configured to charge or discharge the capacitor during only the on-time period.
• According to yet another embodiment, a method (e.g., as implemented according toFIG. 7) for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the method includes processing information associated with the sensed signal, generating a first current signal based on at least information associated with the sensed signal, generating a second current signal, processing information associated with the first current signal and the second current signal, and generating a voltage signal, by at least a capacitor, based on at least information associated with the first current signal and the second current signal. Moreover, the method includes processing information associated with the voltage signal and the sensed signal, generating a comparison signal (e.g., the signal743) based on at least information associated with the voltage signal and the sensed signal, receiving at least the comparison signal, generating a modulation signal based on at least information associated with the comparison signal, receiving the modulation signal, and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least one or more switching periods, and the first current signal represents the inductor current. Each of the one or more switching periods includes at least an on-time period. For each of the one or more switching periods, the process for processing information associated with the first current signal and the second current signal includes discharging or charging the capacitor with the first current signal during only the on-time period, and charging or discharging the capacitor with the second current signal during only the on-time period.
• According to yet another embodiment, a system (e.g., as implemented according toFIG. 8 and/orFIG. 9) for providing at least an output current to one or more light emitting diodes includes a transconductance amplifier (e.g., thecomponent886 and/or the component986) configured to receive a sensed signal and also receive a predetermined voltage signal (e.g., thesignal891 and/or the signal991) through a first switch (e.g., thecomponent880 and/or the component980). The sensed signal is associated with an inductor current flowing through an inductor coupled to a second switch (e.g., thecomponent4820 and/or the component4920), and the transconductance amplifier is further configured to generate a current signal (e.g., thesignal889 and/or the signal989). Additionally, the system includes a capacitor coupled to the transconductance amplifier and configured to generate a voltage signal (e.g., thesignal883 and/or the signal983), and a comparator configured to process information associated with the voltage signal and the sensed signal and generate a comparison signal (e.g., thesignal843 and/or the signal943) based on at least information associated with the voltage signal and the sensed signal. Moreover, the system includes a modulation-signal generator (e.g., thecomponent854 and/or the component954) configured to receive at least the comparison signal and generate a modulation signal (e.g., thesignal857 and/or the signal957), and a gate driver configured to receive the modulation signal and output a drive signal to the second switch. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period for the second switch. The transconductance amplifier (e.g., thecomponent886 and/or the component986) is further configured to, for each of the one or more switching periods, receive at least a predetermined voltage signal only during the on-time period. The current signal (e.g., thesignal889 and/or the signal989) is configured to charge or discharge the capacitor.
• According to yet another embodiment, a method (e.g., as implemented according toFIG. 8 and/orFIG. 9) for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the method includes processing information associated with the sensed signal and a predetermined voltage signal (e.g., thesignal891 and/or the signal991), generating a current signal based on at least information associated with the sensed signal and the predetermined voltage signal, and processing information associated with the current signal. Moreover, the method includes generating a voltage signal, by at least a capacitor, based on at least information associated with the current signal, processing information associated with the voltage signal and the sensed signal, and generating a comparison signal based on at least information associated with the voltage signal and the sensed signal. Also, the method includes receiving at least the comparison signal, generating a modulation signal based on at least information associated with the comparison signal, receiving the modulation signal, and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period. The process for receiving at least a sensed signal includes, for each of the one or more switching periods, receiving at least the predetermined voltage signal during only the on-time period. Also, the process for processing information associated with the current signal includes charging or discharging the capacitor with the current signal (e.g., thesignal889 and/or the signal989).
• According to yet another embodiment, a system (e.g., as implemented according toFIG. 10) for providing at least an output current to one or more light emitting diodes includes a first sampling-and-holding and voltage-to-current-conversion component (e.g., thecomponents1062 and1066) configured to receive at least a sensed signal and generate a first current signal (e.g., the signal1067). The sensed signal is associated with an inductor current flowing through an inductor coupled to a first switch. Additionally, the system includes a second sampling-and-holding and voltage-to-current-conversion component (e.g., thecomponents1064 and1068) configured to receive at least the sensed signal and generate a second current signal (e.g., the signal1069), and a signal-amplification and voltage-to-current-conversion component (e.g., thecomponents1086 and1088) configured to receive at least the sensed signal and generate a third current signal (e.g., the signal1089), a current-signal generator configured to generate a fourth current signal (e.g., the signal1061), and a capacitor coupled to the current-signal generator, coupled through a second switch to the first sampling-and-holding and voltage-to-current-conversion component and the second sampling-and-holding and voltage-to-current-conversion component, and coupled through a third switch to the signal-amplification and voltage-to-current-conversion component, the capacitor being configured to generate a first voltage signal (e.g., the signal1083). Moreover, the system includes a multiplier component (e.g., the component1096) configured to process information associated with the first voltage signal (e.g., the signal1083) and a second voltage signal (e.g., the signal1093) and generate a multiplication signal based on at least information associated with the first voltage signal and the second voltage signal. Also, the system includes a comparator (e.g., the component1042) configured to receive the multiplication signal and the sensed signal and generate a comparison signal (e.g., the signal1043) based on at least information associated with the multiplication signal and the sensed signal, a modulation-signal generator (e.g., the component1054) configured to receive at least the comparison signal and generate a modulation signal (e.g., the signal1057), and a gate driver configured to receive the modulation signal and output a drive signal to the first switch. The drive signal is associated with at least a plurality of switching periods, and each of the one or more switching periods includes at least an on-time period for the first switch and a demagnetization period for a demagnetization process. The first current signal represents the inductor current at the beginning of the on-time period, the second current signal represents the inductor current at the end of the on-time period, and the third current signal represents the inductor current. For the plurality of switching periods, the first current signal and the second current signal are configured to discharge or charge the capacitor during only the demagnetization period, the third current signal is configured to discharge or charge the capacitor during only the on-time period, and the fourth current signal is configured to charge or discharge the capacitor during the switching period.
• According to yet another embodiment, a method (e.g., as implemented according toFIG. 10) for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the method includes processing information associated with the sensed signal, and generating a first current signal, a second current signal, and a third current signal based on at least information associated with the sensed signal. Moreover, the method includes generating a fourth current signal, processing information associated with the first current signal, the second current signal, the third current signal, and the fourth current signal, and generating a first voltage signal, by at least a capacitor, based on at least information associated with the first current signal, the second current signal, the third current signal, and the fourth current signal. Also, the method includes processing information associated with the first voltage signal and a second voltage signal, generating a multiplication signal based on at least information associated with the first voltage signal and the second voltage signal, receiving the multiplication signal and the sensed signal, and generating a comparison signal based on at least information associated with the multiplication signal and the sensed signal. Additionally, the method includes receiving at least the comparison signal, generating a modulation signal based on at least information associated with the comparison signal, receiving the modulation signal, and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least a plurality of switching periods, and each of the plurality of switching periods includes at least an on-time period and a demagnetization period. The first current signal represents the inductor current at the beginning of the on-time period, the second current signal represents the inductor current at the end of the on-time period, and the third current signal represents the inductor current. For each of the plurality of switching periods, the process for processing information associated with the first current signal, the second current signal, the third current signal, and the fourth current signal includes discharging or charging the capacitor with the first current signal and the second current signal during only the demagnetization period, discharging or charging the capacitor with the third current signal during only the on-time period, and charging or discharging the capacitor with the fourth current signal during the switching period.
• According to yet another embodiment, a system (e.g., as implemented according toFIG. 11) for providing at least an output current to one or more light emitting diodes includes a transconductance amplifier (e.g., the component1186) configured to receive a sensed signal and also receive a predetermined voltage signal (e.g., the signal1191) through a first switch (e.g., the component1180). The sensed signal is associated with an inductor current flowing through an inductor coupled to a second switch (e.g., the component5120), and the transconductance amplifier (e.g., the component1186) is further configured to generate a current signal (e.g., the signal1189). Additionally, the system includes a capacitor (e.g., the component1190) coupled to the transconductance amplifier and configured to generate a voltage signal (e.g., the signal1183), and a comparator configured to process information associated with the voltage signal (e.g., the signal1183) and a ramping signal (e.g., the signal1193) and generate a comparison signal (e.g., the signal1143) based on at least information associated with the voltage signal and the ramping signal. Moreover, the system includes a modulation-signal generator (e.g., the component1154) configured to receive at least the comparison signal and generate a modulation signal (e.g., the signal1157), and a gate driver configured to receive the modulation signal and output a drive signal to the second switch. The drive signal is associated with at least one or more switching periods, each of the one or more switching periods including at least an on-time period for the second switch. The transconductance amplifier (e.g., the component1186) is further configured to, for each of the one or more switching periods, receive at least a predetermined voltage signal only during the on-time period. The current signal (e.g., the signal1189) is configured to charge or discharge the capacitor.
• According to yet another embodiment, a method (e.g., as implemented according toFIG. 11) for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the method includes processing information associated with the sensed signal and a predetermined voltage signal (e.g., the signal1191), generating a current signal based on at least information associated with the sensed signal and the predetermined voltage signal, processing information associated with the current signal, and generating a voltage signal, by at least a capacitor, based on at least information associated with the current signal. Moreover, the method includes processing information associated with the voltage signal and a ramping signal (e.g., the signal1193), generating a comparison signal (e.g., the signal1143) based on at least information associated with the voltage signal and the ramping signal, receiving at least the comparison signal, and generating a modulation signal based on at least information associated with the comparison signal. Also, the method includes receiving the modulation signal and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period. The process for receiving at least a sensed signal includes, for each of the one or more switching periods, receiving at least a predetermined voltage signal only during the on-time period, and the process for processing information associated with the current signal includes charging or discharging the capacitor with the current signal (e.g., the signal1189).
• According to yet another embodiment, a system (e.g., as implemented according toFIG. 12) for providing at least an output current to one or more light emitting diodes includes a transconductance amplifier (e.g., the component1286) configured to receive a sensed signal and also receive a predetermined voltage signal (e.g., the signal1291) through a first switch (e.g., the component1280). The sensed signal is associated with an inductor current flowing through an inductor coupled to a second switch, and the transconductance amplifier (e.g., the component1286) is further configured to generate a current signal (e.g., the signal1289). Additionally, the system includes a capacitor coupled to the transconductance amplifier and configured to generate a first voltage signal (e.g., the signal1283), and a multiplier component (e.g., the component1296) configured to process information associated with the first voltage signal and a second voltage signal and generate a multiplication signal based on at least information associated with the first voltage signal and the second voltage signal. Moreover, the system includes a comparator (e.g., the component1242) configured to receive the multiplication signal and the sensed signal and generate a comparison signal based on at least information associated with the multiplication signal and the sensed signal, a modulation-signal generator (e.g., the component1254) configured to receive at least the comparison signal and generate a modulation signal (e.g., the signal1257), and a gate driver configured to receive the modulation signal and output a drive signal to the second switch. The drive signal is associated with at least one or more switching periods, each of the one or more switching periods including at least an on-time period for the second switch. The transconductance amplifier (e.g., the component1286) is further configured to, for each of the one or more switching periods, receive at least a predetermined voltage signal during only the on-time period. The current signal (e.g., the signal1289) is configured to charge or discharge the capacitor.
• According to yet another embodiment, a method (e.g., as implemented according toFIG. 12) for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the method includes processing information associated with the sensed signal and a predetermined voltage signal (e.g., the signal1291), generating a current signal based on at least information associated with the sensed signal and the predetermined voltage signal, processing information associated with the current signal, and generating a first voltage signal (e.g., the signal1283), by at least a capacitor, based on at least information associated with the current signal. Moreover, the method includes processing information associated with the first voltage signal and a second voltage signal (e.g., the signal1293), generating a multiplication signal based on at least information associated with the first voltage signal and the second voltage signal, receiving the multiplication signal and the sensed signal, and generating a comparison signal based on at least information associated with the multiplication signal and the sensed signal. Also, the method includes receiving at least the comparison signal, generating a modulation signal based on at least information associated with the comparison signal, receiving the modulation signal, and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period. The process for receiving at least a sensed signal includes, for each of the one or more switching periods, receiving at least a predetermined voltage signal during only the on-time period, and the process for processing information associated with the current signal includes charging or discharging the capacitor with the current signal (e.g., the signal1289).
• According to yet another embodiment, a system (e.g., as implemented according toFIG. 5) for providing at least an output current to one or more light emitting diodes includes a first signal processing component configured to receive at least a sensed signal and generate a first signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the system includes a second signal processing component configured to generate a second signal, an integrator component configured to receive the first signal and the second signal and generate a third signal, a comparator configured to process information associated with the third signal and the sensed signal and generate a comparison signal based on at least information associated with the third signal and the sensed signal. Moreover, the system includes a signal generator configured to receive at least the comparison signal and generate a modulation signal, and a gate driver configured to receive the modulation signal and output a drive signal to the switch. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period for the switch and a demagnetization period for a demagnetization process. The first signal processing component is further configured to, for each of the one or more switching periods, sample the sensed signal at the middle of the on-time period, hold the sampled sensed signal representing the inductor current at the middle of the on-time period, and generate the first signal representing a sum of a first multiplication result and a second multiplication result based on at least information associated with the held and sampled sensed signal. For each of the one or more switching periods, the second signal represents the switching period multiplied by a predetermined current magnitude. The integrator component is further configured to integrate period-by-period differences between the first signal and the second signal for a plurality of switching periods, and the third signal represents the integrated period-by-period differences. The integrated period-by-period differences are smaller than a predetermined threshold in magnitude.
• According to yet another embodiment, a method (e.g., as implemented according toFIG. 5) for providing at least an output current to one or more light emitting diodes includes receiving at least a sensed signal. The sensed signal is associated with an inductor current flowing through an inductor coupled to a switch. Additionally, the method includes processing information associated with the sensed signal, generating a first signal based on at least information associated with the sensed signal, generating a second signal, receiving the first signal and the second signal, processing information associated with the first signal and the second signal, and generating a third signal based on at least information associated with the first signal and the second signal. Moreover, the method includes processing information associated with the third signal and the sensed signal, generating a comparison signal based on at least information associated with the third signal and the sensed signal, receiving at least the comparison signal, and generating a modulation signal based on at least information associated with the comparison signal. Also, the method includes receiving the modulation signal, and outputting a drive signal based on at least information associated with the modulation signal. The drive signal is associated with at least one or more switching periods, and each of the one or more switching periods includes at least an on-time period for the switch and a demagnetization period for a demagnetization process. The process for processing information associated with the sensed signal includes, for each of the one or more switching periods, sampling the sensed signal at the middle of the on-time period, and holding the sampled sensed signal representing the inductor current at the middle of the on-time period. For each of the one or more switching periods, the first signal represents a sum of a first multiplication result and a second multiplication result generated based on at least information associated with the held and sampled sensed signal, and the second signal represents the switching period multiplied by a predetermined current magnitude. The process for processing information associated with the first signal and the second signal includes integrating period-by-period differences between the first signal and the second signal for a plurality of switching periods, and the third signal represents the integrated period-by-period differences. The integrated period-by-period differences are smaller than a predetermined threshold in magnitude.
• Although specific embodiments of the present invention have been described, it will be understood by those of skill in the art that there are other embodiments that are equivalent to the described embodiments. Accordingly, it is to be understood that the invention is not to be limited by the specific illustrated embodiments, but only by the scope of the appended claims.

Claims (13)

1.-32. (canceled)

33. A system for providing at least an output current to one or more light emitting diodes, the system comprising:

a signal-amplification and voltage-to-current-conversion component configured to receive at least a sensed signal and generate a first current signal, the sensed signal being associated with an inductor current flowing through an inductor coupled to a first switch;

a current-signal generator configured to generate a second current signal;

a capacitor coupled to the current-signal generator, and coupled through a second switch to the signal-amplification and voltage-to-current-conversion component, the capacitor being configured to generate a voltage signal;

a comparator configured to process information associated with the voltage signal and the sensed signal and generate a comparison signal based on at least information associated with the voltage signal and the sensed signal;

a modulation-signal generator configured to receive at least the comparison signal and generate a modulation signal; and

a gate driver configured to receive the modulation signal and output a drive signal to the first switch;

wherein:

the drive signal is associated with at least one or more switching periods, each of the one or more switching periods including at least an on-time period for the first switch; and

the first current signal represents the inductor current;

wherein for each of the one or more switching periods,

the first current signal is configured to discharge or charge the capacitor during only the on-time period; and

the second current signal is configured to charge or discharge the capacitor during only the on-time period.

34. The system ofclaim 33 wherein the signal-amplification and voltage-to-current-conversion component includes a signal-amplification component and a voltage-to-current-conversion component.

35. The system ofclaim 33 wherein:

the signal-amplification and voltage-to-current-conversion component, the current-signal generator, the comparator, the modulation-signal generator, and the gate driver are located on a chip; and

the capacitor is located off the chip.

36. The system ofclaim 33 is configured to regulate an output current at a predetermined constant level in a continuous conduction mode.

37. A method for providing at least an output current to one or more light emitting diodes, the method comprising:

receiving at least a sensed signal, the sensed signal being associated with an inductor current flowing through an inductor coupled to a switch;

processing information associated with the sensed signal;

generating a first current signal based on at least information associated with the sensed signal;

generating a second current signal;

processing information associated with the first current signal and the second current signal;

generating a voltage signal, by at least a capacitor, based on at least information associated with the first current signal and the second current signal;

processing information associated with the voltage signal and the sensed signal;

generating a comparison signal based on at least information associated with the voltage signal and the sensed signal;

receiving at least the comparison signal;

generating a modulation signal based on at least information associated with the comparison signal;

receiving the modulation signal;

outputting a drive signal based on at least information associated with the modulation signal;

wherein:

the drive signal is associated with at least one or more switching periods, each of the one or more switching periods including at least an on-time period; and

the first current signal represents the inductor current;

wherein for each of the one or more switching periods, the process for processing information associated with the first current signal and the second current signal includes:

discharging or charging the capacitor with the first current signal during only the on-time period; and

charging or discharging the capacitor with the second current signal during only the on-time period.

38. A system for providing at least an output current to one or more light emitting diodes, the system comprising:

a transconductance amplifier configured to receive a sensed signal and also receive a predetermined voltage signal through a first switch, the sensed signal being associated with an inductor current flowing through an inductor coupled to a second switch, the transconductance amplifier being further configured to generate a current signal;

a capacitor coupled to the transconductance amplifier and configured to generate a voltage signal;

a comparator configured to process information associated with the voltage signal and the sensed signal and generate a comparison signal based on at least information associated with the voltage signal and the sensed signal;

a modulation-signal generator configured to receive at least the comparison signal and generate a modulation signal; and

a gate driver configured to receive the modulation signal and output a drive signal to the second switch;

wherein:

the drive signal is associated with at least one or more switching periods, each of the one or more switching periods including at least an on-time period for the second switch;

the transconductance amplifier is further configured to, for each of the one or more switching periods, receive at least a predetermined voltage signal only during the on-time period; and

the current signal is configured to charge or discharge the capacitor.

39. The system ofclaim 38 wherein:

the transconductance amplifier, the comparator, the modulation-signal generator, and the gate driver are located on a chip; and

the capacitor is located off the chip.

40. The system ofclaim 38 is configured to regulate an output current at a predetermined constant level in a continuous conduction mode and a critical conduction mode.

41. The system ofclaim 38 is configured to regulate an output current at a predetermined constant level in a continuous conduction mode.

42. The system ofclaim 38 is configured to regulate an output current at a predetermined constant level in a critical conduction mode.

43. A method for providing at least an output current to one or more light emitting diodes, the method comprising:

receiving at least a sensed signal, the sensed signal being associated with an inductor current flowing through an inductor coupled to a switch;

processing information associated with the sensed signal and a predetermined voltage signal;

generating a current signal based on at least information associated with the sensed signal and the predetermined voltage signal;

processing information associated with the current signal;

generating a voltage signal, by at least a capacitor, based on at least information associated with the current signal;

processing information associated with the voltage signal and the sensed signal;

generating a comparison signal based on at least information associated with the voltage signal and the sensed signal;

receiving at least the comparison signal;

generating a modulation signal based on at least information associated with the comparison signal;

receiving the modulation signal;

outputting a drive signal based on at least information associated with the modulation signal;

wherein:

the drive signal is associated with at least one or more switching periods, each of the one or more switching periods including at least an on-time period; and

the process for receiving at least a sensed signal includes, for each of the one or more switching periods, receiving at least the predetermined voltage signal during only the on-time period;

wherein the process for processing information associated with the current signal includes charging or discharging the capacitor with the current signal.

44.-73. (canceled)

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